Look into full URL spec to see whether it is MP4

content/renderer/render_frame_impl.cc

 // Copyright 2013 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 "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 778 matching lines @@
 //
 // Note that HLS and MP4 detection are pre-redirect and path-based. It is
 // possible to load such a URL and find different content.
 bool UseWebMediaPlayerImpl(const GURL& url) {
   // WMPI does not support HLS.
   if (media::MediaCodecUtil::IsHLSURL(url))
     return false;
 
   // Don't use WMPI if the container likely contains a codec we can't decode in
   // software and platform decoders are not available.
-  if (base::EndsWith(url.path(), ".mp4",
-                     base::CompareCase::INSENSITIVE_ASCII) &&
-      !media::HasPlatformDecoderSupport()) {
-    return false;
+  if (!media::HasPlatformDecoderSupport()) {
+    // Assume "mp4" means H264.

[piman, 2016/09/16 01:45:00]

nit: please add a link to the bug. This logic is very suspicious at first
glance, the bug explains a bit more - it sounds like this is a temporary fix?

[Tima Vaisburd, 2016/09/16 19:04:22]

Done.

+    if (base::ToLowerASCII(url.spec()).find("mp4") != std::string::npos)
+      return false;
   }
 
   // Indicates if the Android MediaPlayer should be used instead of WMPI.
   if (GetContentClient()->renderer()->ShouldUseMediaPlayerForURL(url))
     return false;
 
   // Otherwise enable WMPI if indicated via experiment or command line.
   return media::IsUnifiedMediaPipelineEnabled();
 }
 #endif  // defined(OS_ANDROID)
@@ skipping 5538 matching lines @@
   // event target. Potentially a Pepper plugin will receive the event.
   // In order to tell whether a plugin gets the last mouse event and which it
   // is, we set |pepper_last_mouse_event_target_| to null here. If a plugin gets
   // the event, it will notify us via DidReceiveMouseEvent() and set itself as
   // |pepper_last_mouse_event_target_|.
   pepper_last_mouse_event_target_ = nullptr;
 #endif
 }
 
 }  // namespace content