OpaqueBrowserFrameViewPlatformSpecific::Create no longer returns NULL.

This avoids duplicating the default logic for all of its methods.
Previously, every time a method was called, we had to test for NULL and
assume the default value for that method (even though the default method
implementation already exists; it was never used). Now the caller
assumes platform_observer_ is non-NULL (via a DCHECK) and it is the base
class's responsibility to provide default methods.

Review URL: https://codereview.chromium.org/124893002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243819 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/frame/opaque_browser_frame_view.cc

@@ -428,10 +428,8 @@ void OpaqueBrowserFrameView::Observe(
 
 bool OpaqueBrowserFrameView::ShouldShowWindowIcon() const {
   views::WidgetDelegate* delegate = frame()->widget_delegate();
-  // ShouldShowTitleBar defaults to true.
-  if (platform_observer_ && !platform_observer_->ShouldShowTitleBar())
-    return false;
-  return delegate && delegate->ShouldShowWindowIcon();
+  return platform_observer_->ShouldShowTitleBar() && delegate &&
+         delegate->ShouldShowWindowIcon();
 }
 
 bool OpaqueBrowserFrameView::ShouldShowWindowTitle() const {
@@ -439,10 +437,8 @@ bool OpaqueBrowserFrameView::ShouldShowWindowTitle() const {
   // a window is being destroyed.
   // See more discussion at http://crosbug.com/8958
   views::WidgetDelegate* delegate = frame()->widget_delegate();
-  // ShouldShowTitleBar defaults to true.
-  if (platform_observer_ && !platform_observer_->ShouldShowTitleBar())
-    return false;
-  return delegate && delegate->ShouldShowWindowTitle();
+  return platform_observer_->ShouldShowTitleBar() && delegate &&
+         delegate->ShouldShowWindowTitle();
 }
 
 base::string16 OpaqueBrowserFrameView::GetWindowTitle() const {
@@ -470,8 +466,6 @@ gfx::Size OpaqueBrowserFrameView::GetBrowserViewMinimumSize() const {
 bool OpaqueBrowserFrameView::ShouldShowCaptionButtons() const {
   if (!OpaqueBrowserFrameViewLayout::ShouldAddDefaultCaptionButtons())
     return false;
-  if (!platform_observer_)
-    return true;
   return platform_observer_->ShouldShowCaptionButtons();
 }
 

chrome/browser/ui/views/frame/opaque_browser_frame_view_platform_specific.cc

@@ -13,7 +13,7 @@ OpaqueBrowserFrameViewPlatformSpecific*
 OpaqueBrowserFrameViewPlatformSpecific::Create(
     OpaqueBrowserFrameView* view,
     OpaqueBrowserFrameViewLayout* layout) {
-  return 0;
+  return new OpaqueBrowserFrameViewPlatformSpecific();
 }
 
 #endif

chrome/browser/ui/views/frame/opaque_browser_frame_view_platform_specific.h

@@ -13,8 +13,7 @@ class OpaqueBrowserFrameViewPlatformSpecific {
  public:
   virtual ~OpaqueBrowserFrameViewPlatformSpecific() {}
 
-  // Builds an observer for |view| and |layout|. This method returns NULL on
-  // platforms which don't need configuration.
+  // Builds an observer for |view| and |layout|.
   static OpaqueBrowserFrameViewPlatformSpecific* Create(
       OpaqueBrowserFrameView* view,
       OpaqueBrowserFrameViewLayout* layout);