Tab Audio Mirroring: WebContentsAudioInputStream is a new implementation which represents the lifet…

content/browser/renderer_host/media/web_contents_tracker.cc

+// Copyright (c) 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/browser/renderer_host/media/web_contents_tracker.h"
+
+#include "base/message_loop_proxy.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/web_contents.h"
+
+namespace content {
+
+WebContentsTracker::WebContentsTracker() {}
+
+WebContentsTracker::~WebContentsTracker() {
+  DCHECK(!web_contents()) << "BUG: Still observering!";
+}
+
+void WebContentsTracker::Start(int render_process_id, int render_view_id,
+                               const ChangeCallback& callback) {
+  DCHECK(!message_loop_ || message_loop_->BelongsToCurrentThread());
+
+  message_loop_ = base::MessageLoopProxy::current();
+  DCHECK(message_loop_);
+  callback_ = callback;
+
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&WebContentsTracker::LookUpAndObserveWebContents, this,
+                 render_process_id, render_view_id));
+}
+
+void WebContentsTracker::Stop() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+
+  callback_.Reset();
+
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&WebContentsTracker::Observe, this,
+                 static_cast<WebContents*>(NULL)));
+}
+
+void WebContentsTracker::OnWebContentsChangeEvent() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  WebContents* const wc = web_contents();
+  RenderViewHost* const rvh = wc ? wc->GetRenderViewHost() : NULL;
+  RenderProcessHost* const rph = rvh ? rvh->GetProcess() : NULL;
+
+  const int render_process_id = rph ? rph->GetID() : MSG_ROUTING_NONE;
+  const int render_view_id = rvh ? rvh->GetRoutingID() : MSG_ROUTING_NONE;
+
+  message_loop_->PostTask(FROM_HERE,
+      base::Bind(&WebContentsTracker::MaybeDoCallback, this,
+                 render_process_id, render_view_id));
+}
+
+void WebContentsTracker::MaybeDoCallback(int render_process_id,
+                                         int render_view_id) {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+
+  if (!callback_.is_null())
+    callback_.Run(render_process_id, render_view_id);
+}
+
+void WebContentsTracker::LookUpAndObserveWebContents(int render_process_id,
+                                                     int render_view_id) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  RenderViewHost* const rvh =
+      RenderViewHost::FromID(render_process_id, render_view_id);
+  DVLOG_IF(1, !rvh) << "RenderViewHost::FromID("
+                    << render_process_id << ", " << render_view_id
+                    << ") returned NULL.";
+  Observe(rvh ? WebContents::FromRenderViewHost(rvh) : NULL);
+  DVLOG_IF(1, !web_contents())
+      << "WebContents::FromRenderViewHost(" << rvh << ") returned NULL.";
+
+  OnWebContentsChangeEvent();
+}
+
+void WebContentsTracker::RenderViewReady() {
+  OnWebContentsChangeEvent();
+}
+
+void WebContentsTracker::AboutToNavigateRenderView(RenderViewHost* rvh) {
+  OnWebContentsChangeEvent();
+}
+
+void WebContentsTracker::DidNavigateMainFrame(
+    const LoadCommittedDetails& details, const FrameNavigateParams& params) {
+  OnWebContentsChangeEvent();
+}
+
+void WebContentsTracker::WebContentsDestroyed(WebContents* web_contents) {
+  OnWebContentsChangeEvent();
+}
+
+}  // namespace content