Move the initialization of System Profile in early startup behind the flag "UmaBackgroundSessions".

It allows a comparison of UMA data lost when Chrome is running in background
and reduced mode.

Bug: 954310
Change-Id: I2d7a6ac4d4eb5b53e043cbbe2e1e217a3a9a1838
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787463Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Xi Han <hanxi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694310}

chrome/android/javatests/src/org/chromium/chrome/browser/ServicificationBackgroundServiceTest.java

@@ -119,7 +119,7 @@ public final class ServicificationBackgroundServiceTest {
     @Test
     @LargeTest
     @Feature({"ServicificationStartup"})
-    @CommandLineFlags.Add("force-fieldtrials=*Foo/Bar")
+    @CommandLineFlags.Add({"force-fieldtrials=*Foo/Bar", "enable-features=UMABackgroundSessions"})
     public void testHistogramsPersistedWithServiceManagerOnlyStart() {
         createBrowserMetricsSpareFile();
         Assert.assertTrue(mSpareFile.exists());

chrome/app/chrome_main_delegate.cc

@@ -116,6 +116,7 @@
 
 #if defined(OS_ANDROID)
 #include "base/android/java_exception_reporter.h"
+#include "chrome/browser/android/chrome_feature_list.h"
 #include "chrome/browser/android/crash/pure_java_exception_handler.h"
 #include "chrome/common/chrome_descriptors.h"
 #else  // defined(OS_ANDROID)
@@ -548,7 +549,13 @@ void ChromeMainDelegate::PostEarlyInitialization(bool is_running_tests) {
 
   if (base::FeatureList::IsEnabled(
           features::kWriteBasicSystemProfileToPersistentHistogramsFile)) {
-    startup_data_->RecordCoreSystemProfile();
+    bool record = true;
+#if defined(OS_ANDROID)
+    record =
+        base::FeatureList::IsEnabled(chrome::android::kUmaBackgroundSessions);
+#endif
+    if (record)
+      startup_data_->RecordCoreSystemProfile();
   }
 }