Media: add metrics for orientation lock when video goes fullscreen.

This is recording how often the metadata are already available/needed
and the result of the lock attempt.

BUG=670455
R=asvitkine@chromium.org, zqzhang@chromium.org

Review-Url: https://codereview.chromium.org/2581603003
Cr-Commit-Position: refs/heads/master@{#438958}

third_party/WebKit/Source/core/html/shadow/MediaControlsOrientationLockDelegate.cpp

@@ -8,6 +8,7 @@
 #include "core/frame/ScreenOrientationController.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/page/ChromeClient.h"
+#include "platform/Histogram.h"
 #include "public/platform/WebScreenInfo.h"
 #include "public/platform/modules/screen_orientation/WebLockOrientationCallback.h"
 
@@ -15,6 +16,41 @@ namespace blink {
 
 namespace {
 
+// These values are used for histograms. Do not reorder.
+enum class MetadataAvailabilityMetrics {
+  Available = 0,  // Available when lock was attempted.
+  Missing = 1,    // Missing when lock was attempted.
+  Received = 2,   // Received after being missing in order to lock.
+
+  // Keep at the end.
+  Max = 3
+};
+
+// These values are used for histograms. Do not reorder.
+enum class LockResultMetrics {
+  AlreadyLocked = 0,  // Frame already has a lock.
+  Portrait = 1,       // Locked to portrait.
+  Landscape = 2,      // Locked to landscape.
+
+  // Keep at the end.
+  Max = 3
+};
+
+void recordMetadataAvailability(MetadataAvailabilityMetrics metrics) {
+  DEFINE_STATIC_LOCAL(
+      EnumerationHistogram, metadataHistogram,
+      ("Media.Video.FullscreenOrientationLock.MetadataAvailability",
+       static_cast<int>(MetadataAvailabilityMetrics::Max)));
+  metadataHistogram.count(static_cast<int>(metrics));
+}
+
+void recordLockResult(LockResultMetrics metrics) {
+  DEFINE_STATIC_LOCAL(EnumerationHistogram, lockResultHistogram,
+                      ("Media.Video.FullscreenOrientationLock.LockResult",
+                       static_cast<int>(LockResultMetrics::Max)));
+  lockResultHistogram.count(static_cast<int>(metrics));
+}
+
 // WebLockOrientationCallback implementation that will not react to a success
 // nor a failure.
 class DummyScreenOrientationCallback : public WebLockOrientationCallback {
@@ -43,22 +79,36 @@ void MediaControlsOrientationLockDelegate::maybeLockOrientation() {
   DCHECK(m_state != State::MaybeLockedFullscreen);
 
   if (videoElement().getReadyState() == HTMLMediaElement::kHaveNothing) {
+    recordMetadataAvailability(MetadataAvailabilityMetrics::Missing);
     m_state = State::PendingMetadata;
     return;
   }
 
+  if (m_state == State::PendingMetadata)
+    recordMetadataAvailability(MetadataAvailabilityMetrics::Received);
+  else
+    recordMetadataAvailability(MetadataAvailabilityMetrics::Available);
+
   m_state = State::MaybeLockedFullscreen;
 
   if (!document().frame())
     return;
 
   auto controller = ScreenOrientationController::from(*document().frame());
-  if (controller->maybeHasActiveLock())
+  if (controller->maybeHasActiveLock()) {
+    recordLockResult(LockResultMetrics::AlreadyLocked);
     return;
+  }
 
-  controller->lock(computeOrientationLock(),
+  WebScreenOrientationLockType orientationLock = computeOrientationLock();
+  controller->lock(orientationLock,
                    WTF::wrapUnique(new DummyScreenOrientationCallback));
   m_shouldUnlockOrientation = true;
+
+  if (orientationLock == WebScreenOrientationLockLandscape)
+    recordLockResult(LockResultMetrics::Landscape);
+  else
+    recordLockResult(LockResultMetrics::Portrait);
 }
 
 void MediaControlsOrientationLockDelegate::maybeUnlockOrientation() {

tools/metrics/histograms/histograms.xml

@@ -25579,6 +25579,23 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Video.FullscreenOrientationLock.LockResult"
+    enum="VideoFullscreenOrientationLockResult">
+  <owner>mlamouri@chromium.org</owner>
+  <summary>
+    Result of the orientation lock attempt when a video enters fullscreen.
+  </summary>
+</histogram>
+
+<histogram name="Media.Video.FullscreenOrientationLock.MetadataAvailability"
+    enum="VideoFullscreenOrientationLockMetadataAvailability">
+  <owner>mlamouri@chromium.org</owner>
+  <summary>
+    Status of the metadata when attempting to lock the screen orientation for a
+    fullscreen video.
+  </summary>
+</histogram>
+
 <histogram name="Media.Video.KeyFrameDistance" units="ms">
   <owner>avayvod@chromium.org</owner>
   <owner>dalecurtis@chromium.org</owner>
@@ -106225,6 +106242,18 @@ value.
   <int value="9" label="UYVY"/>
 </enum>
 
+<enum name="VideoFullscreenOrientationLockMetadataAvailability" type="int">
+  <int value="0" label="Available"/>
+  <int value="1" label="Missing"/>
+  <int value="2" label="Received (after Missing)"/>
+</enum>
+
+<enum name="VideoFullscreenOrientationLockResult" type="int">
+  <int value="0" label="Already locked, no attempt"/>
+  <int value="1" label="Portrait"/>
+  <int value="2" label="Landscape"/>
+</enum>
+
 <enum name="VideoPixelFormat" type="int">
   <obsolete>
     Deprecated as of 05/2015. Substituted by VideoFormat.