[Picture-in-Picture] Treat WebContents-scoped controller per-tab.

Currently, the PictureInPictureWindowController is reset and torn down
whenever a new video goes into Picture-in-Picture mode. This is less
than ideal since the PictureInPictureWindowController is attached and
scoped to the lifetime of a WebContents via WebContentsUserData.

Rather, we should allow the natural teardown of the controller when
the initiator tabs is destroyed.

BUG: 823172
Change-Id: I7e13b8bf45899fd4ff4b3dbd34781d04ab15dc1d
Reviewed-on: https://chromium-review.googlesource.com/1034194
Commit-Queue: apacible <apacible@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555415}

chrome/browser/ui/browser.cc

@@ -1409,10 +1409,13 @@ void Browser::OnDidBlockFramebust(content::WebContents* web_contents,
 
 void Browser::UpdatePictureInPictureSurfaceId(const viz::SurfaceId& surface_id,
                                               const gfx::Size& natural_size) {
-  if (!pip_window_controller_)
-    pip_window_controller_.reset(
+  if (!pip_window_controller_ ||
+      pip_window_controller_->GetInitiatorWebContents() !=
+          tab_strip_model_->GetActiveWebContents()) {
+    pip_window_controller_ =
         content::PictureInPictureWindowController::GetOrCreateForWebContents(
-            tab_strip_model_->GetActiveWebContents()));
+            tab_strip_model_->GetActiveWebContents());
+  }
   pip_window_controller_->EmbedSurface(surface_id, natural_size);
   pip_window_controller_->Show();
 }

chrome/browser/ui/browser.h

@@ -1001,8 +1001,12 @@ class Browser : public TabStripModelObserver,
 
   std::unique_ptr<chrome::BrowserCommandController> command_controller_;
 
-  std::unique_ptr<content::PictureInPictureWindowController>
-      pip_window_controller_;
+  // |pip_window_controller_| is held as a SupportsUserData attachment on the
+  // content::WebContents, and thus scoped to the lifetime of the initiator
+  // content::WebContents.
+  // The current active Picture-in-Picture controller is held in case of
+  // updates to the relevant viz::SurfaceId.
+  content::PictureInPictureWindowController* pip_window_controller_ = nullptr;
 
   // True if the browser window has been shown at least once.
   bool window_has_shown_;

content/browser/picture_in_picture/picture_in_picture_window_controller_impl.cc

@@ -101,6 +101,10 @@ void PictureInPictureWindowControllerImpl::UpdateLayerBounds() {
     embedder_->UpdateLayerBounds();
 }
 
+WebContents* PictureInPictureWindowControllerImpl::GetInitiatorWebContents() {
+  return initiator_;
+}
+
 bool PictureInPictureWindowControllerImpl::TogglePlayPause() {
   DCHECK(window_ && window_->IsActive());
 

content/browser/picture_in_picture/picture_in_picture_window_controller_impl.h

@@ -39,6 +39,7 @@ class PictureInPictureWindowControllerImpl
                                    const gfx::Size& natural_size) override;
   CONTENT_EXPORT OverlayWindow* GetWindowForTesting() override;
   CONTENT_EXPORT void UpdateLayerBounds() override;
+  CONTENT_EXPORT WebContents* GetInitiatorWebContents() override;
   CONTENT_EXPORT bool TogglePlayPause() override;
 
  private:

content/public/browser/picture_in_picture_window_controller.h

@@ -39,6 +39,7 @@ class PictureInPictureWindowController {
                             const gfx::Size& natural_size) = 0;
   virtual OverlayWindow* GetWindowForTesting() = 0;
   virtual void UpdateLayerBounds() = 0;
+  virtual WebContents* GetInitiatorWebContents() = 0;
 
   // Commands.
   // Returns true if the player is active (i.e. currently playing) after this