Fix crash when Background Memory metrics task is scheduled immediately.

It is scheduled with a random delay between 0ms and 59999ms. When it is
exactly 0, the delayed task is actually executed as a regular task,
and since it is scheduled just before the task that starts native,
it runs without native, causing a crash.

Moving recordMemoryUsageWithRandomDelay() to after native is initialized
fixes the issue.

https://chromium-review.googlesource.com/c/chromium/src/+/1880172 fixed
this issue incorrectly. This is a corrected version.

Bug: 1017130
Change-Id: Ia79a4c3dcf639ffc01d1eacbfe53d082419c8ed7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1884272Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Reviewed-by: Xi Han <hanxi@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710011}

chrome/android/java/src/org/chromium/chrome/browser/background_task_scheduler/NativeBackgroundTask.java

@@ -129,19 +129,23 @@ public abstract class NativeBackgroundTask implements BackgroundTask {
             final Runnable rescheduleRunnable) {
         if (isNativeLoadedInFullBrowserMode()) {
             mRunningInServiceManagerOnlyMode = false;
-            recordMetrics();
+            BackgroundTaskSchedulerExternalUma.reportNativeTaskStarted(
+                    mTaskId, mRunningInServiceManagerOnlyMode);
+            recordMemoryUsageWithRandomDelay(mRunningInServiceManagerOnlyMode);
             PostTask.postTask(UiThreadTaskTraits.DEFAULT, startWithNativeRunnable);
             return;
         }
 
         boolean wasInServiceManagerOnlyMode = isNativeLoadedInServiceManagerOnlyMode();
         mRunningInServiceManagerOnlyMode = supportsServiceManagerOnly();
-        recordMetrics();
+        BackgroundTaskSchedulerExternalUma.reportNativeTaskStarted(
+                mTaskId, mRunningInServiceManagerOnlyMode);
 
         final BrowserParts parts = new EmptyBrowserParts() {
             @Override
             public void finishNativeInitialization() {
                 PostTask.postTask(UiThreadTaskTraits.DEFAULT, startWithNativeRunnable);
+                recordMemoryUsageWithRandomDelay(mRunningInServiceManagerOnlyMode);
             }
             @Override
             public boolean startServiceManagerOnly() {
@@ -257,12 +261,6 @@ public abstract class NativeBackgroundTask implements BackgroundTask {
         return getBrowserStartupController().isRunningInServiceManagerMode();
     }
 
-    private void recordMetrics() {
-        BackgroundTaskSchedulerExternalUma.reportNativeTaskStarted(
-                mTaskId, mRunningInServiceManagerOnlyMode);
-        recordMemoryUsageWithRandomDelay(mRunningInServiceManagerOnlyMode);
-    }
-
     @VisibleForTesting
     protected BrowserStartupController getBrowserStartupController() {
         return BrowserStartupController.get(LibraryProcessType.PROCESS_BROWSER);