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 recordMetrics() to after native is initialized fixes the issue.

Bug: 1017130
Change-Id: Ica5d0a125b93433bd2291a6c73ac30d3fd890aa8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880172
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709269}

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

@@ -136,12 +136,12 @@ public abstract class NativeBackgroundTask implements BackgroundTask {
 
         boolean wasInServiceManagerOnlyMode = isNativeLoadedInServiceManagerOnlyMode();
         mRunningInServiceManagerOnlyMode = supportsServiceManagerOnly();
-        recordMetrics();
 
         final BrowserParts parts = new EmptyBrowserParts() {
             @Override
             public void finishNativeInitialization() {
                 PostTask.postTask(UiThreadTaskTraits.DEFAULT, startWithNativeRunnable);
+                recordMetrics();
             }
             @Override
             public boolean startServiceManagerOnly() {