Mitigate upload failure when app is backgrounded.

iOS closes an app’s network connections when the app is backgrounded. This can cause an in-progress upload request to fail. We can mitigate this by requesting additional background execution time using the `UIApplication` background task APIs.

BUG=b:130302235

Change-Id: Ifd8e14ca82c736ad7dd60dcdd0d4bbcabb76f5ad
Signed-off-by: Darren Mo <darrenmo@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/2251020
Reviewed-by: Mark Mentovai <mark@chromium.org>

src/client/ios/Breakpad.xcodeproj/project.pbxproj

@@ -59,6 +59,8 @@
 		AACBBE4A0F95108600F1A2B1 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = AACBBE490F95108600F1A2B1 /* Foundation.framework */; };
 		CF6D547D1F9E6FFE00E95174 /* long_string_dictionary.cc in Sources */ = {isa = PBXBuildFile; fileRef = CF6D547C1F9E6FFE00E95174 /* long_string_dictionary.cc */; };
 		CF706DC11F7C6EFB002C54C7 /* long_string_dictionary.h in Headers */ = {isa = PBXBuildFile; fileRef = CF706DC01F7C6EFB002C54C7 /* long_string_dictionary.h */; };
+		E69213D8265202570071B04F /* HTTPRequest.h in Headers */ = {isa = PBXBuildFile; fileRef = E69213D6265202570071B04F /* HTTPRequest.h */; };
+		E69213D9265202570071B04F /* HTTPRequest.m in Sources */ = {isa = PBXBuildFile; fileRef = E69213D7265202570071B04F /* HTTPRequest.m */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -116,6 +118,8 @@
 		CF6D547C1F9E6FFE00E95174 /* long_string_dictionary.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = long_string_dictionary.cc; sourceTree = "<group>"; };
 		CF706DC01F7C6EFB002C54C7 /* long_string_dictionary.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = long_string_dictionary.h; sourceTree = "<group>"; };
 		D2AAC07E0554694100DB518D /* libBreakpad.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libBreakpad.a; sourceTree = BUILT_PRODUCTS_DIR; };
+		E69213D6265202570071B04F /* HTTPRequest.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = HTTPRequest.h; sourceTree = "<group>"; };
+		E69213D7265202570071B04F /* HTTPRequest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = HTTPRequest.m; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -289,6 +293,8 @@
 			children = (
 				16C7CC88147D4A4300776EAD /* GTMLogger.h */,
 				16C7CC89147D4A4300776EAD /* GTMLogger.m */,
+				E69213D6265202570071B04F /* HTTPRequest.h */,
+				E69213D7265202570071B04F /* HTTPRequest.m */,
 				16C7CC8A147D4A4300776EAD /* HTTPMultipartUpload.h */,
 				16C7CC8B147D4A4300776EAD /* HTTPMultipartUpload.m */,
 				16C7CC93147D4A4300776EAD /* file_id.cc */,
@@ -335,6 +341,7 @@
 				16C7CE1A147D4A4300776EAD /* minidump_file_writer.h in Headers */,
 				16C7CE41147D4A4300776EAD /* convert_UTF.h in Headers */,
 				16C7CE78147D4A4300776EAD /* GTMLogger.h in Headers */,
+				E69213D8265202570071B04F /* HTTPRequest.h in Headers */,
 				16C7CE7A147D4A4300776EAD /* HTTPMultipartUpload.h in Headers */,
 				16C7CE84147D4A4300776EAD /* file_id.h in Headers */,
 				16C7CE86147D4A4300776EAD /* macho_id.h in Headers */,
@@ -416,6 +423,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				16C7CCCD147D4A4300776EAD /* Breakpad.mm in Sources */,
+				E69213D9265202570071B04F /* HTTPRequest.m in Sources */,
 				16C7CDE9147D4A4300776EAD /* ConfigFile.mm in Sources */,
 				16C7CDF5147D4A4300776EAD /* breakpad_nlist_64.cc in Sources */,
 				16C7CDF7147D4A4300776EAD /* dynamic_images.cc in Sources */,

src/common/mac/HTTPRequest.m

@@ -32,8 +32,26 @@
 #include <Availability.h>
 #include <AvailabilityMacros.h>
 
+#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && defined(__IPHONE_7_0) && \
+     __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_7_0)
+#import <UIKit/UIKit.h>
+#define HAS_BACKGROUND_TASK_API 1
+#else
+#define HAS_BACKGROUND_TASK_API 0
+#endif
+
 #import "encoding_util.h"
 
+#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && defined(__IPHONE_7_0) && \
+     __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_7_0) ||                  \
+    (defined(MAC_OS_X_VERSION_MIN_REQUIRED) &&                             \
+     defined(MAC_OS_X_VERSION_10_11) &&                                    \
+     MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_11)
+#define USE_NSURLSESSION 1
+#else
+#define USE_NSURLSESSION 0
+#endif
+
 // As -[NSURLConnection sendSynchronousRequest:returningResponse:error:] has
 // been deprecated with iOS 9.0 / OS X 10.11 SDKs, this function re-implements
 // it using -[NSURLSession dataTaskWithRequest:completionHandler:] which is
@@ -41,20 +59,17 @@
 static NSData* SendSynchronousNSURLRequest(NSURLRequest* req,
                                            NSURLResponse** outResponse,
                                            NSError** outError) {
-#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && defined(__IPHONE_7_0) && \
+#if USE_NSURLSESSION
-     __IPHONE_OS_VERSION_MIN_REQUIRED >= __IPHONE_7_0) ||                  \
-    (defined(MAC_OS_X_VERSION_MIN_REQUIRED) &&                             \
-     defined(MAC_OS_X_VERSION_10_11) &&                                    \
-     MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_11)
   __block NSData* result = nil;
   __block NSError* error = nil;
   __block NSURLResponse* response = nil;
   dispatch_semaphore_t waitSemaphone = dispatch_semaphore_create(0);
+
   NSURLSessionConfiguration* config =
       [NSURLSessionConfiguration defaultSessionConfiguration];
   [config setTimeoutIntervalForRequest:240.0];
   NSURLSession* session = [NSURLSession sessionWithConfiguration:config];
-  [[session
+  NSURLSessionDataTask *task = [session
       dataTaskWithRequest:req
         completionHandler:^(NSData* data, NSURLResponse* resp, NSError* err) {
           if (outError)
@@ -64,19 +79,59 @@ static NSData* SendSynchronousNSURLRequest(NSURLRequest* req,
           if (err == nil)
             result = [data retain];
           dispatch_semaphore_signal(waitSemaphone);
-        }] resume];
+        }];
+  [task resume];
+
+#if HAS_BACKGROUND_TASK_API
+  // Used to guard against ending the background task twice, which UIKit
+  // considers to be an error.
+  __block BOOL isBackgroundTaskActive = YES;
+  __block UIBackgroundTaskIdentifier backgroundTaskIdentifier =
+      UIBackgroundTaskInvalid;
+  backgroundTaskIdentifier = [UIApplication.sharedApplication
+      beginBackgroundTaskWithName:@"Breakpad Upload"
+                expirationHandler:^{
+                  if (!isBackgroundTaskActive) {
+                    return;
+                  }
+                  isBackgroundTaskActive = NO;
+
+                  [task cancel];
+                  [UIApplication.sharedApplication
+                      endBackgroundTask:backgroundTaskIdentifier];
+                }];
+#endif  // HAS_BACKGROUND_TASK_API
+
   dispatch_semaphore_wait(waitSemaphone, DISPATCH_TIME_FOREVER);
   dispatch_release(waitSemaphone);
+
+#if HAS_BACKGROUND_TASK_API
+  if (backgroundTaskIdentifier != UIBackgroundTaskInvalid) {
+    // Dispatch to main queue in order to synchronize access to
+    // `isBackgroundTaskActive` with the background task expiration handler,
+    // which is always run on the main thread.
+    dispatch_async(dispatch_get_main_queue(), ^{
+      if (!isBackgroundTaskActive) {
+        return;
+      }
+      isBackgroundTaskActive = NO;
+
+      [UIApplication.sharedApplication
+          endBackgroundTask:backgroundTaskIdentifier];
+    });
+  }
+#endif  // HAS_BACKGROUND_TASK_API
+
   if (outError)
     *outError = [error autorelease];
   if (outResponse)
     *outResponse = [response autorelease];
   return [result autorelease];
-#else
+#else  // USE_NSURLSESSION
   return [NSURLConnection sendSynchronousRequest:req
                                returningResponse:outResponse
                                            error:outError];
-#endif
+#endif  // USE_NSURLSESSION
 }
 
 @implementation HTTPRequest