[ScreenOrientation] Fix a possible crash point in ScreenOrientationProvider.

content/public/browser/screen_orientation_provider.cc

 // Copyright 2014 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/public/browser/screen_orientation_provider.h"
 
 #include "base/callback_helpers.h"
-#include "base/optional.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/screen_orientation_delegate.h"
 #include "content/public/browser/web_contents.h"
 #include "third_party/WebKit/public/platform/modules/screen_orientation/WebLockOrientationError.h"
 
 namespace content {
 
 using device::mojom::ScreenOrientationLockResult;
 
 ScreenOrientationDelegate* ScreenOrientationProvider::delegate_ = nullptr;
 
 ScreenOrientationProvider::ScreenOrientationProvider(WebContents* web_contents)
     : WebContentsObserver(web_contents), lock_applied_(false) {}
 
 ScreenOrientationProvider::~ScreenOrientationProvider() {
 }
 
 void ScreenOrientationProvider::LockOrientation(
     blink::WebScreenOrientationLockType orientation,
     const LockOrientationCallback& callback) {
-  // ScreenOrientation should have cancelled all pending request at this point.
-  DCHECK(on_result_callback_.is_null());
-  DCHECK(!pending_lock_orientation_.has_value());
-  on_result_callback_ = callback;
+  // Cancel any pending lock request.
+  NotifyLockResult(ScreenOrientationLockResult::
+                       SCREEN_ORIENTATION_LOCK_RESULT_ERROR_CANCELED);
+  // Record new pending lock request.
+  pending_callback_ = callback;
 
   if (!delegate_ || !delegate_->ScreenOrientationProviderSupported()) {
     NotifyLockResult(ScreenOrientationLockResult::
                          SCREEN_ORIENTATION_LOCK_RESULT_ERROR_NOT_AVAILABLE);
     return;
   }
 
   if (delegate_->FullScreenRequired(web_contents())) {
     RenderViewHostImpl* rvhi =
         static_cast<RenderViewHostImpl*>(web_contents()->GetRenderViewHost());
@@ skipping 29 matching lines @@
   if (LockMatchesCurrentOrientation(orientation)) {
     NotifyLockResult(
         ScreenOrientationLockResult::SCREEN_ORIENTATION_LOCK_RESULT_SUCCESS);
     return;
   }
 
   pending_lock_orientation_ = orientation;
 }
 
 void ScreenOrientationProvider::UnlockOrientation() {
+  // Cancel any pending lock request.
+  NotifyLockResult(ScreenOrientationLockResult::
+                       SCREEN_ORIENTATION_LOCK_RESULT_ERROR_CANCELED);
+
   if (!lock_applied_ || !delegate_)
     return;
 
   delegate_->Unlock(web_contents());
 
   lock_applied_ = false;
-  pending_lock_orientation_.reset();
 }
 
 void ScreenOrientationProvider::OnOrientationChange() {
   if (!pending_lock_orientation_.has_value())
     return;
 
   if (LockMatchesCurrentOrientation(pending_lock_orientation_.value())) {
-    DCHECK(!on_result_callback_.is_null());
+    DCHECK(!pending_callback_.is_null());
     NotifyLockResult(
         ScreenOrientationLockResult::SCREEN_ORIENTATION_LOCK_RESULT_SUCCESS);
   }
 }
 
 void ScreenOrientationProvider::NotifyLockResult(
     ScreenOrientationLockResult result) {
-  if (on_result_callback_.is_null()) {
-    pending_lock_orientation_.reset();
-    return;
+  if (!pending_callback_.is_null()) {
+    base::ResetAndReturn(&pending_callback_).Run(result);
   }

[kinuko, 2017/01/23 02:39:50]

nit: no need of block for one-line body

[leonhsl(Using Gerrit), 2017/01/23 02:47:10]

Got it, as I've sent this CL to CQ now so I will address this in the follow-up
CL which will also change this file :) Thanks!

-  base::ResetAndReturn(&on_result_callback_).Run(result);
   pending_lock_orientation_.reset();
 }
 
 void ScreenOrientationProvider::SetDelegate(
     ScreenOrientationDelegate* delegate) {
   delegate_ = delegate;
 }
 
 void ScreenOrientationProvider::DidToggleFullscreenModeForTab(
     bool entered_fullscreen, bool will_cause_resize) {
@@ skipping 79 matching lines @@
     case blink::WebScreenOrientationLockDefault:
       NOTREACHED();
       return false;
   }
 
   NOTREACHED();
   return false;
 }
 
 } // namespace content