Defer media loading while on cellular networks.

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 48 matching lines @@
 #include "core/html/track/TextTrackList.h"
 #include "core/html/track/VideoTrack.h"
 #include "core/html/track/VideoTrackList.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/layout/LayoutVideo.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/DeprecatedPaintLayerCompositor.h"
 #include "core/loader/FrameLoader.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/page/ChromeClient.h"
+#include "core/page/NetworkStateNotifier.h"
 #include "platform/ContentType.h"
 #include "platform/Logging.h"
 #include "platform/MIMETypeFromURL.h"
 #include "platform/MIMETypeRegistry.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/UserGestureIndicator.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/weborigin/SecurityOrigin.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebContentDecryptionModule.h"
@@ skipping 1850 matching lines @@
 
 void HTMLMediaElement::setPreload(const AtomicString& preload)
 {
     WTF_LOG(Media, "HTMLMediaElement::setPreload(%p, %s)", this, preload.utf8().data());
     setAttribute(preloadAttr, preload);
 }
 
 WebMediaPlayer::Preload HTMLMediaElement::preloadType() const
 {
     const AtomicString& preload = fastGetAttribute(preloadAttr);
+
+    WebMediaPlayer::Preload preloadType;
     if (equalIgnoringCase(preload, "none")) {
         UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadNone);
-        return WebMediaPlayer::PreloadNone;
-    }
-    if (equalIgnoringCase(preload, "metadata")) {
+        preloadType = WebMediaPlayer::PreloadNone;
+    } else if (equalIgnoringCase(preload, "metadata")) {
         UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadMetadata);
-        return WebMediaPlayer::PreloadMetaData;
-    }
-    if (equalIgnoringCase(preload, "auto")) {
+        preloadType = WebMediaPlayer::PreloadMetaData;
+    } else if (equalIgnoringCase(preload, "auto")) {
         UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadAuto);
-        return WebMediaPlayer::PreloadAuto;
+        preloadType = WebMediaPlayer::PreloadAuto;
+    } else {
+        UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadDefault);
+
+        // "The attribute's missing value default is user-agent defined, though the
+        // Metadata state is suggested as a compromise between reducing server load
+        // and providing an optimal user experience."
+
+        // The spec does not define an invalid value default:
+        // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28950
+
+        // TODO(philipj): Try to make "metadata" the default preload state:
+        // https://crbug.com/310450
+        preloadType = WebMediaPlayer::PreloadAuto;
     }
 
-    // "The attribute's missing value default is user-agent defined, though the
-    // Metadata state is suggested as a compromise between reducing server load
-    // and providing an optimal user experience."
+    // Force preload to none for cellular connections.
+    if (networkStateNotifier().connectionType() == WebConnectionTypeCellular)

[philipj_slow, 2015/10/01 09:24:07]

Make this an early return at the top, which should make this diff very small.

[philipj_slow, 2015/10/01 09:49:49]

As pointed out in the other review, this should then have its own use counter.

[DaleCurtis, 2015/10/20 21:56:51]

Done -- but to be clear, doing this ruins the rest of the use counter stats;
they will now go unlogged for all cellular traffic.

[philipj_slow, 2015/10/21 11:11:29]

Right, anyone looking at the stats has to understand that it's not a measurement
of what attribute values appear in the page, but rather of what the effective
preload state is and why. (That is the information I would find valuable in
estimating the risk in changing the behavior of any given preload state.)

+        preloadType = WebMediaPlayer::PreloadNone;
 
-    // The spec does not define an invalid value default:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28950
-
-    // TODO(philipj): Try to make "metadata" the default preload state:
-    // https://crbug.com/310450
-    UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadDefault);
-    return WebMediaPlayer::PreloadAuto;
+    return preloadType;
 }
 
 WebMediaPlayer::Preload HTMLMediaElement::effectivePreloadType() const
 {
     return autoplay() ? WebMediaPlayer::PreloadAuto : preloadType();
 }
 
 void HTMLMediaElement::play()
 {
     WTF_LOG(Media, "HTMLMediaElement::play(%p)", this);
@@ skipping 1841 matching lines @@
     visitor->trace(m_client);
 }
 
 DEFINE_TRACE(HTMLMediaElement::AudioSourceProviderImpl)
 {
     visitor->trace(m_client);
 }
 #endif
 
 }