Implement all resolution change policies for desktop and tab capture.

content/browser/media/capture/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/media/capture/web_contents_tracker.h"
 
 #include "base/thread_task_runner_handle.h"
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 26 matching lines @@
         BrowserThread::UI, FROM_HERE,
         base::Bind(&WebContentsTracker::StartObservingWebContents, this,
                    render_process_id, main_render_frame_id));
   }
 }
 
 void WebContentsTracker::Stop() {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   callback_.Reset();
+  resize_callback_.Reset();
 
   if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     WebContentsObserver::Observe(NULL);
   } else {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&WebContentsTracker::Observe, this,
                    static_cast<WebContents*>(NULL)));
   }
 }
@@ skipping 14 matching lines @@
   if (!rwh) {
     RenderFrameHostImpl* const rfh =
         static_cast<RenderFrameHostImpl*>(wc->GetMainFrame());
     if (rfh)
       rwh = rfh->GetRenderWidgetHost();
   }
 
   return rwh;
 }
 
+void WebContentsTracker::SetResizeChangeCallback(
+    const ChangeCallback& callback) {
+  DCHECK(!task_runner_.get() || task_runner_->BelongsToCurrentThread());
+  resize_callback_ = callback;
+}
+
+namespace {
+
+// In debug builds, map a non-null RenderWidgetHost pointer to an invalid
+// non-null pointer.  This causes the app to crash if a client of
+// WebContentsTracker later attempts to dereference the pointer when it should
+// not.  See comments for ChangeCallback in the header file.
+RenderWidgetHost* InvalidatePointerInDebugBuilds(RenderWidgetHost* rwh) {

[Wez, 2015/05/15 00:55:42]

See my other comments on how to avoid the need for this hack. :)

[miu, 2015/05/15 21:14:01]

Acknowledged.

+#ifndef NDEBUG
+  if (rwh)
+    return static_cast<RenderWidgetHost*>(nullptr) + 1;
+  else
+    return nullptr;
+#else
+  return rwh;
+#endif
+}
+
+}  // namespace
+
 void WebContentsTracker::OnPossibleTargetChange(bool force_callback_run) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   RenderWidgetHost* const rwh = GetTargetRenderWidgetHost();
   if (rwh == last_target_ && !force_callback_run)
     return;
   DVLOG(1) << "Will report target change from RenderWidgetHost@" << last_target_
            << " to RenderWidgetHost@" << rwh;
   last_target_ = rwh;
 
   if (task_runner_->BelongsToCurrentThread()) {
     MaybeDoCallback(rwh);
   } else {
     task_runner_->PostTask(
         FROM_HERE,
-        base::Bind(&WebContentsTracker::MaybeDoCallback, this, rwh));
+        base::Bind(&WebContentsTracker::MaybeDoCallback,
+                   this,
+                   InvalidatePointerInDebugBuilds(rwh)));
   }
 }
 
 void WebContentsTracker::MaybeDoCallback(RenderWidgetHost* rwh) {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   if (!callback_.is_null())
     callback_.Run(rwh);
+  if (rwh)
+    MaybeDoResizeCallback(rwh);
+}
+
+void WebContentsTracker::MaybeDoResizeCallback(RenderWidgetHost* rwh) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  if (!resize_callback_.is_null())
+    resize_callback_.Run(rwh);
 }
 
 void WebContentsTracker::StartObservingWebContents(int render_process_id,
                                                    int main_render_frame_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   Observe(WebContents::FromRenderFrameHost(RenderFrameHost::FromID(
       render_process_id, main_render_frame_id)));
   DVLOG_IF(1, !web_contents())
       << "Could not find WebContents associated with main RenderFrameHost "
       << "referenced by render_process_id=" << render_process_id
       << ", routing_id=" << main_render_frame_id;
 
   OnPossibleTargetChange(true);
 }
 
 void WebContentsTracker::RenderFrameDeleted(
     RenderFrameHost* render_frame_host) {
   OnPossibleTargetChange(false);
 }
 
 void WebContentsTracker::RenderFrameHostChanged(RenderFrameHost* old_host,
                                                 RenderFrameHost* new_host) {
   OnPossibleTargetChange(false);
 }
 
+void WebContentsTracker::MainFrameWasResized(bool width_changed) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  RenderWidgetHost* const rwh = GetTargetRenderWidgetHost();
+  if (!rwh)
+    return;
+
+  if (task_runner_->BelongsToCurrentThread()) {
+    MaybeDoResizeCallback(rwh);
+  } else {
+    task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&WebContentsTracker::MaybeDoResizeCallback,
+                   this,
+                   InvalidatePointerInDebugBuilds(rwh)));
+  }
+
+}
+
 void WebContentsTracker::WebContentsDestroyed() {
   Observe(NULL);
   OnPossibleTargetChange(false);
 }
 
 void WebContentsTracker::DidShowFullscreenWidget(int routing_id) {
   OnPossibleTargetChange(false);
 }
 
 void WebContentsTracker::DidDestroyFullscreenWidget(int routing_id) {
   OnPossibleTargetChange(false);
 }
 
 }  // namespace content