[Android WebAPK] Add WebappSplashScreen.hidingAnimation trace event

This CL:
- Adds the "WebappSplashScreen.hidingAnimation" trace event which
  tracks the start and stop of the splash screen hide animation.
- Removes the "WebappSplashScreen" trace event because it is redudant
  with "WebappActivity.showSplash" and
  "WebappSplashScreen.hidingAnimation".

BUG=945784

Change-Id: If4e6513a288867b028c5a797d41ef32d754708e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1547068Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Peter Kotwicz <pkotwicz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646597}

chrome/android/java/src/org/chromium/chrome/browser/webapps/SameActivityWebappSplashDelegate.java

@@ -86,7 +86,7 @@ public class SameActivityWebappSplashDelegate implements WebappSplashDelegate {
         mSplashScreen = new FrameLayout(context);
         mSplashScreen.setBackgroundColor(backgroundColor);
         mParentView.addView(mSplashScreen);
-        startSplashscreenTraceEvents();
+        recordTraceEventsShowedSplash();
 
         if (webappInfo.isForWebApk()) {
             initializeLayout(webappInfo, backgroundColor, ((WebApkInfo) webappInfo).splashIcon());
@@ -125,6 +125,7 @@ public class SameActivityWebappSplashDelegate implements WebappSplashDelegate {
         assert mIsSplashVisible;
 
         mIsSplashVisible = false;
+        recordTraceEventsStartedHidingSplash();
         mSplashScreen.animate().alpha(0f).withEndAction(new Runnable() {
             @Override
             public void run() {
@@ -134,7 +135,7 @@ public class SameActivityWebappSplashDelegate implements WebappSplashDelegate {
                     mWebApkNetworkErrorObserver = null;
                 }
 
-                finishSplashscreenTraceEvents();
+                recordTraceEventsFinishedHidingSplash();
                 mTab = null;
                 mSplashScreen = null;
                 finishedHidingCallback.run();
@@ -225,14 +226,17 @@ public class SameActivityWebappSplashDelegate implements WebappSplashDelegate {
         if (mNativeLoaded) mUmaCache.commitMetrics();
     }
 
-    private void startSplashscreenTraceEvents() {
-        TraceEvent.startAsync("WebappSplashScreen", hashCode());
+    private void recordTraceEventsShowedSplash() {
         SingleShotOnDrawListener.install(mParentView,
                 () -> { TraceEvent.startAsync("WebappSplashScreen.visible", hashCode()); });
     }
 
-    private void finishSplashscreenTraceEvents() {
-        TraceEvent.finishAsync("WebappSplashScreen", hashCode());
+    private void recordTraceEventsStartedHidingSplash() {
+        TraceEvent.startAsync("WebappSplashScreen.hidingAnimation", hashCode());
+    }
+
+    private void recordTraceEventsFinishedHidingSplash() {
+        TraceEvent.finishAsync("WebappSplashScreen.hidingAnimation", hashCode());
         SingleShotOnDrawListener.install(mParentView,
                 () -> { TraceEvent.finishAsync("WebappSplashScreen.visible", hashCode()); });
     }