Defer media loading while on cellular networks.

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

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
index 614c6ce029563ab390b6395af1f1e283eed2f81d..11bc920351abb0c55bc7c83775645041964f2124 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -66,6 +66,7 @@
 #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"
@@ -247,6 +248,11 @@ static bool canLoadURL(const KURL& url, const ContentType& contentType, const St
     return false;
 }
 
+static bool shouldForcePreloadNoneForCellularNetwork()
+{
+    return networkStateNotifier().connectionType() == WebConnectionTypeCellular;
+}
+
 void HTMLMediaElement::recordAutoplayMetric(AutoplayMetrics metric)
 {
     Platform::current()->histogramEnumeration("Blink.MediaElement.Autoplay", metric, NumberOfAutoplayMetrics);
@@ -1936,30 +1942,37 @@ void HTMLMediaElement::setPreload(const AtomicString& preload)
 WebMediaPlayer::Preload HTMLMediaElement::preloadType() const
 {
     const AtomicString& preload = fastGetAttribute(preloadAttr);
+
+    WebMediaPlayer::Preload preloadType;
+    const bool forcePreloadNone = shouldForcePreloadNoneForCellularNetwork();
     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 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 = forcePreloadNone ? WebMediaPlayer::PreloadNone : WebMediaPlayer::PreloadAuto;

[watk, 2015/09/30 01:21:52]

It might be clearer to just set to Auto here, and let the override take place
below? Then you can inline the call to shouldForcePre...()

[DaleCurtis, 2015/09/30 01:33:44]

Done.

+    }
 
-    // The spec does not define an invalid value default:
-    // https://www.w3.org/Bugs/Public/show_bug.cgi?id=28950
+    if (forcePreloadNone)
+        preloadType = WebMediaPlayer::PreloadNone;
 
-    // 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