Fix a linker error when enable_webrtc is false on Android

Linker complains an undefined reference to
'content::MediaStreamDispatcher::GetNonScreenCaptureDevices()' when
building Cast for Android with enable_webrtc being false.

BUG=Internal b/37205701

Review-Url: https://codereview.chromium.org/2809803002
Cr-Commit-Position: refs/heads/master@{#463420}

content/renderer/render_view_impl.cc

@@ -2510,6 +2510,7 @@ bool RenderViewImpl::DidTapMultipleTargets(
 }
 
 void RenderViewImpl::SuspendVideoCaptureDevices(bool suspend) {
+#if BUILDFLAG(ENABLE_WEBRTC)
   if (!main_render_frame_)
     return;
 
@@ -2522,6 +2523,7 @@ void RenderViewImpl::SuspendVideoCaptureDevices(bool suspend) {
       media_stream_dispatcher->GetNonScreenCaptureDevices();
   RenderThreadImpl::current()->video_capture_impl_manager()->SuspendDevices(
       video_array, suspend);
+#endif  // BUILDFLAG(ENABLE_WEBRTC)
 }
 #endif  // defined(OS_ANDROID)