Implement all resolution change policies for desktop and tab capture.

content/browser/media/capture/web_contents_tracker.cc

Index: content/browser/media/capture/web_contents_tracker.cc
diff --git a/content/browser/media/capture/web_contents_tracker.cc b/content/browser/media/capture/web_contents_tracker.cc
index a9e161f1ce3fcf2ce299734fb103d805ea574eb5..a72c7bef800faceba4a5f399d7113a1aae17fbc6 100644
--- a/content/browser/media/capture/web_contents_tracker.cc
+++ b/content/browser/media/capture/web_contents_tracker.cc
@@ -44,6 +44,7 @@ void WebContentsTracker::Stop() {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   callback_.Reset();
+  resize_callback_.Reset();
 
   if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     WebContentsObserver::Observe(NULL);
@@ -78,6 +79,31 @@ RenderWidgetHost* WebContentsTracker::GetTargetRenderWidgetHost() const {
   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);
 
@@ -93,7 +119,9 @@ void WebContentsTracker::OnPossibleTargetChange(bool force_callback_run) {
   } else {
     task_runner_->PostTask(
         FROM_HERE,
-        base::Bind(&WebContentsTracker::MaybeDoCallback, this, rwh));
+        base::Bind(&WebContentsTracker::MaybeDoCallback,
+                   this,
+                   InvalidatePointerInDebugBuilds(rwh)));
   }
 }
 
@@ -102,6 +130,15 @@ void WebContentsTracker::MaybeDoCallback(RenderWidgetHost* rwh) {
 
   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,
@@ -128,6 +165,25 @@ void WebContentsTracker::RenderFrameHostChanged(RenderFrameHost* old_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);