customtabs: Send time to first contentful paint to the caller.

chrome/browser/page_load_metrics/observers/android_page_load_metrics_observer.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/page_load_metrics/observers/android_page_load_metrics_observer.h"
+
+#include <string>
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_string.h"
+#include "base/android/scoped_java_ref.h"
+#include "components/page_load_metrics/browser/page_load_metrics_util.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/web_contents.h"
+#include "jni/PageLoadMetrics_jni.h"
+#include "url/gurl.h"
+
+AndroidPageLoadMetricsObserver::AndroidPageLoadMetricsObserver(
+    content::WebContents* web_contents)
+    : web_contents_(web_contents), has_seen_first_contentful_paint_(false) {}
+
+void AndroidPageLoadMetricsObserver::OnTimingUpdate(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& extra_info) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  if (has_seen_first_contentful_paint_ || !timing.first_contentful_paint)
+    return;
+  double first_contentful_paint_ms =
+      timing.first_contentful_paint->InMillisecondsF();
+  base::android::ScopedJavaLocalRef<jobject> java_web_contents =
+      web_contents_->GetJavaWebContents();
+  JNIEnv* env = base::android::AttachCurrentThread();
+  Java_PageLoadMetrics_onFirstContentfulPaintMetricUpdate(
+      env, java_web_contents.obj(), first_contentful_paint_ms);
+  has_seen_first_contentful_paint_ = true;
+}
+
+bool RegisterPageLoadMetricsBindings(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}