Add back RenderFrameHost sanity-check to AudioRendererHost.

content/browser/renderer_host/media/audio_renderer_host.h

Index: content/browser/renderer_host/media/audio_renderer_host.h
diff --git a/content/browser/renderer_host/media/audio_renderer_host.h b/content/browser/renderer_host/media/audio_renderer_host.h
index 7252086657dc01d89cff53846874d7cf4201b9f0..e525512c81883f87cb582c4d37d3e1fd20516d05 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.h
+++ b/content/browser/renderer_host/media/audio_renderer_host.h
@@ -49,6 +49,7 @@
 
 #include "base/atomic_ref_count.h"
 #include "base/gtest_prod_util.h"
+#include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/process/process.h"
@@ -129,6 +130,14 @@ class CONTENT_EXPORT AudioRendererHost : public BrowserMessageFilter {
                               const AudioOutputDeviceInfo& device_info)>
       OutputDeviceInfoCB;
 
+  // The type of a function that is run on the UI thread to check whether the
+  // routing IDs reference a valid RenderFrameHost. The function then runs
+  // |callback| on the IO thread with true/false if valid/invalid.
+  using ValidateRenderFrameIdFunction =

[o1ka, 2016/07/11 10:35:50]

probably #ifdef this as well?

[miu, 2016/07/14 21:36:12]

Based on past experience, we generally don't conditionally compile typedefs in
Chromium when they do not contain platform-specific types. There should be no
additional code generation resulting from this.

+      void (*)(int render_process_id,
+               int render_frame_id,
+               const base::Callback<void(bool)>& callback);
+
   ~AudioRendererHost() override;
 
   // Methods called on IO thread ----------------------------------------------
@@ -186,7 +195,8 @@ class CONTENT_EXPORT AudioRendererHost : public BrowserMessageFilter {
   void DoCreateStream(int stream_id,
                       int render_frame_id,
                       const media::AudioParameters& params,
-                      const std::string& device_unique_id);
+                      const std::string& device_unique_id,
+                      bool render_frame_id_is_valid);
 
   // Complete the process of creating an audio stream. This will set up the
   // shared memory or shared socket in low latency mode and send the
@@ -237,6 +247,15 @@ class CONTENT_EXPORT AudioRendererHost : public BrowserMessageFilter {
   // |stream_id| has started.
   bool IsAuthorizationStarted(int stream_id);
 
+#if DCHECK_IS_ON()
+  // Called from AudioRendererHostTest to override the function that checks for
+  // the existence of the RenderFrameHost at stream creation time.
+  void set_render_frame_id_validate_function_for_testing(
+      ValidateRenderFrameIdFunction function) {
+    validate_render_frame_id_function_ = function;
+  }
+#endif  // DCHECK_IS_ON()
+
   // ID of the RenderProcessHost that owns this instance.
   const int render_process_id_;
 
@@ -263,6 +282,13 @@ class CONTENT_EXPORT AudioRendererHost : public BrowserMessageFilter {
   // The second element contains the unique ID of the authorized device.
   std::map<int, std::pair<bool, std::string>> authorizations_;
 
+#if DCHECK_IS_ON()
+  // When DCHECKs are turned on, AudioRendererHost will call this function on
+  // the UI thread to validate render frame IDs. A default is set by the
+  // constructor, but this can be overridden by unit tests.
+  ValidateRenderFrameIdFunction validate_render_frame_id_function_;

[o1ka, 2016/07/11 10:35:50]

AudioRendererHost is exported from content.
Is a situation possible that ARH user which is built with DCHECKs off is linked
with ARH built with DCHECKs on, or vise verse? (I've seen problems like that in
other projects, they are not easy to debug.)

[miu, 2016/07/14 21:36:12]

This shouldn't be an issue in the Chromium project. I'm not aware of any support
for linking code built with different build_config.

+#endif  // DCHECK_IS_ON()
+
   // The maximum number of simultaneous streams during the lifetime of this
   // host. Reported as UMA stat at shutdown.
   size_t max_simultaneous_streams_;