media: Add experimental feature to enable Mojo CDM on desktop Chromium

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 3ca56c4a5a62aba13b2e82e4fe3d29e1ef8da93e..d5995d7d4eb8a5f945c57fb0127efe0cc94d603b 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -6775,18 +6775,21 @@ media::mojom::RemoterFactory* RenderFrameImpl::GetRemoterFactory() {
 #endif
 
 media::CdmFactory* RenderFrameImpl::GetCdmFactory() {
+  DCHECK(frame_);
+
   if (cdm_factory_)
     return cdm_factory_.get();
 
-#if BUILDFLAG(ENABLE_MOJO_CDM)
-  cdm_factory_.reset(new media::MojoCdmFactory(GetMediaInterfaceProvider()));
-  return cdm_factory_.get();
-#endif  //  BUILDFLAG(ENABLE_MOJO_CDM)
-
 #if BUILDFLAG(ENABLE_PEPPER_CDMS)
-  DCHECK(frame_);
-  cdm_factory_.reset(
-      new RenderCdmFactory(base::Bind(&PepperCdmWrapperImpl::Create, frame_)));
+  static_assert(BUILDFLAG(ENABLE_MOJO_CDM),
+                "Mojo CDM should always be enabled when PPAPI CDM is enabled");
+  if (base::FeatureList::IsEnabled(media::kMojoCdm))
+    cdm_factory_.reset(new media::MojoCdmFactory(GetMediaInterfaceProvider()));
+  else

[jam, 2017/05/24 00:36:33]

nit: brace brackets per style guide

+    cdm_factory_.reset(new RenderCdmFactory(
+        base::Bind(&PepperCdmWrapperImpl::Create, frame_)));
+#elif BUILDFLAG(ENABLE_MOJO_CDM)
+  cdm_factory_.reset(new media::MojoCdmFactory(GetMediaInterfaceProvider()));
 #endif  // BUILDFLAG(ENABLE_PEPPER_CDMS)
 
 #if BUILDFLAG(ENABLE_MEDIA_REMOTING)

[jrummell, 2017/05/23 22:23:28]

Is it possible for cdm_factory_ to get set twice? Should this be first above,
then #elif ENABLE_PEPPER_CDMS?

[xhwang, 2017/05/23 22:31:12]

The RemotingCdmFactory actually wraps the cdm_factory_ set above, so this has to
be after the above block.