Disable HW H264 decoder for Win7 & add enable flag

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 5bb4178595ab0fbbf1aa5bd8ee63b94e2a608332..620ece1a53d4050a9e8c0d3b3a5ad1637c23bf19 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -1010,6 +1010,10 @@ const char kEnableWin32kLockDownMimeTypes[] =
 // Enables experimental hardware acceleration for VP8/VP9 video decoding.
 const char kEnableAcceleratedVpxDecode[] = "enable-accelerated-vpx-decode";
 
+// Enables H264 HW decode acceleration for WebRtc on Win 7.
+const char kEnableWin7WebRtcHWH264Decoding[] =
+    "enable-win7-webrtc-hw-h264-decoding";
+
 // DirectWrite FontCache is shared by browser to renderers using shared memory.
 // This switch allows us to pass the shared memory handle to the renderer.
 const char kFontCacheSharedHandle[] = "font-cache-shared-handle";