[ios] Add crashed_after_app_will_terminate synthetic crash reports flag

According to Stability.iOS.UTE.MobileSessionAppWillTerminateWasReceived
UMA it's not uncommon to have a UTE after appWillTerminate callback.

Bug: None
Change-Id: I20b9e581b8dadb11d2b3e8b7f1c770f5ae1df650
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627049
Auto-Submit: Eugene But <eugenebut@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843072}

components/previous_session_info/previous_session_info_private.h

@@ -26,6 +26,7 @@
 @property(nonatomic, assign) NSInteger memoryFootprint;
 @property(nonatomic, assign) NSInteger tabCount;
 @property(nonatomic, assign) NSInteger OTRTabCount;
+@property(nonatomic, assign) BOOL applicationWillTerminateWasReceived;
 
 + (void)resetSharedInstanceForTesting;
 

ios/chrome/browser/crash_report/synthetic_crash_report_util.mm

@@ -131,6 +131,11 @@ void CreateSyntheticCrashReportForUte(
         base::NumberToString(previous_session.memoryFootprint));
   }
 
+  if (previous_session.applicationWillTerminateWasReceived) {
+    AppendConfigWithBreakpadServerParam(
+        config, "crashed_after_app_will_terminate", "yes");
+  }
+
   // Write empty minidump file, as Breakpad can't upload config without the
   // minidump.
   base::File minidump_file(

ios/chrome/browser/crash_report/synthetic_crash_report_util_unittest.mm

@@ -40,6 +40,7 @@ TEST_F(SyntheticCrashReportUtilTest, CreateSyntheticCrashReportForUte) {
   NSString* const kOSVersion = @"OSVersion";
   previous_session.OSVersion = kOSVersion;
   previous_session.terminatedDuringSessionRestoration = YES;
+  previous_session.applicationWillTerminateWasReceived = YES;
   NSString* const kURL = @"URL";
   previous_session.reportParameters = @{@"url" : kURL};
   previous_session.sessionStartTime = [NSDate date];
@@ -109,7 +110,7 @@ TEST_F(SyntheticCrashReportUtilTest, CreateSyntheticCrashReportForUte) {
 
   // Verify config file content. Config file has the following format:
   // <Key1>\n<Value1Length>\n<Value1>\n...<KeyN>\n<ValueNLength>\n<ValueN>
-  ASSERT_EQ(58U, config_lines.size())
+  ASSERT_EQ(61U, config_lines.size())
       << "<content>" << config_content << "</content>";
 
   EXPECT_EQ("MinidumpDir", config_lines[0]);
@@ -203,6 +204,11 @@ TEST_F(SyntheticCrashReportUtilTest, CreateSyntheticCrashReportForUte) {
             config_lines[56]);
   EXPECT_EQ(base::NumberToString(kMemoryFootprint), config_lines[57]);
 
+  EXPECT_EQ("BreakpadServerParameterPrefix_crashed_after_app_will_terminate",
+            config_lines[58]);
+  EXPECT_EQ(base::NumberToString(strlen(kYesString)), config_lines[59]);
+  EXPECT_EQ(kYesString, config_lines[60]);
+
   // Read minidump file. It must be empty as there is no stack trace, but
   // Breakpad will not upload config without minidump file.
   base::File minidump_file(minidump_file_path,