Only force preload=none over cellular for http, https, ftp URLs.

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 77aa5fe35409933471eb164bbb4b5be025ecc02e..f132a0780837869915ccc75b990ef7f1cce2d928 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -1908,8 +1908,9 @@ void HTMLMediaElement::setPreload(const AtomicString& preload)
 
 WebMediaPlayer::Preload HTMLMediaElement::preloadType() const
 {
-    // Force preload to none for cellular connections.
-    if (networkStateNotifier().connectionType() == WebConnectionTypeCellular) {
+    // Force preload to none for cellular connections for online resources.

[philipj_slow, 2015/12/16 14:39:05]

I think the idea is right, but that modifying preloadType() depending on
currentSrc isn't quite right. There's a spec issue relevant to this:

https://github.com/whatwg/html/issues/295

My thinking is that the cleanest way to deal with this would be at the point
where preload=none has an effect, in the resource fetch algorithm:
https://html.spec.whatwg.org/multipage/embedded-content.html#concept-media-lo...

In other words, specify the conditions under which those suspend steps should be
skipped, and I think that doing it for just data: and blob: URLs should be OK?
(Carving out an exception for data: and friends seems easier than listing the
normal cases.)

A bit of searching suggests that Android WebView uses file: URLs for local
resources, is that right? That's a bit tricky, because people might implicitly
be using file: for local testing, and it's unfortunate if that should change the
preload behavior...

[Srirama, 2015/12/16 14:54:12]

Should we consider content:// (content providers in android) as well?

[philipj_slow, 2015/12/16 15:25:31]

Does that currently work with media elements?
http://developer.android.com/reference/android/content/ContentResolver.html
looks complicated, does content:// always return a local resource, or could it
redirect to something on the network?

[DaleCurtis, 2015/12/17 00:02:19]

There are a few different injectables AFAIK, WebView has one too:

https://code.google.com/p/chromium/codesearch#chromium/src/media/base/android...

...so I went with an explicit white list of kinda-known network connections
instead (service workers may be serving locally too over http/https, but not
sure how that might be checked).

+    const bool isNetworkURL = m_currentSrc.protocolIsInHTTPFamily() || m_currentSrc.protocolIs("ftp");
+    if (isNetworkURL && networkStateNotifier().connectionType() == WebConnectionTypeCellular) {
         UseCounter::count(document(), UseCounter::HTMLMediaElementPreloadForcedNone);
         return WebMediaPlayer::PreloadNone;
     }