Mac: Make more views adopts ThemedWindowDrawing

Follow up to https://codereview.chromium.org/900613003/.
Make NewTabButton and TabStripBackgroundView adopt ThemedWindowDrawing.

BUG=455955,453996

Review URL: https://codereview.chromium.org/904503003

Cr-Commit-Position: refs/heads/master@{#315061}

chrome/browser/ui/cocoa/new_tab_button.h

@@ -7,12 +7,14 @@
 
 #import <Cocoa/Cocoa.h>
 
+#import "chrome/browser/ui/cocoa/themed_window.h"
+
 // Overrides hit-test behavior to only accept clicks inside the image of the
 // button, not just inside the bounding box. This could be abstracted to general
 // use, but no other buttons are so irregularly shaped with respect to their
 // bounding box.
 
-@interface NewTabButton : NSButton
+@interface NewTabButton : NSButton<ThemedWindowDrawing>
 
 // Returns YES if the given point is over the button.  |point| is in the
 // superview's coordinate system.

chrome/browser/ui/cocoa/new_tab_button.mm

@@ -55,4 +55,14 @@
   return nil;
 }
 
+// ThemedWindowDrawing implementation.
+
+- (void)windowDidChangeTheme {
+  [self setNeedsDisplay:YES];
+}
+
+- (void)windowDidChangeActive {
+  [self setNeedsDisplay:YES];
+}
+
 @end

chrome/browser/ui/cocoa/tabs/tab_strip_background_view.h

@@ -7,11 +7,13 @@
 
 #import <Cocoa/Cocoa.h>
 
+#import "chrome/browser/ui/cocoa/themed_window.h"
+
 // A view that draws the theme image in the top area of the window (behind the
 // tab strip area). It should be arranged so that its z-order is below its
 // overlapping sibling views (window controls, tab strip view, profile button
 // and fullscreen button).
-@interface TabStripBackgroundView : NSView
+@interface TabStripBackgroundView : NSView<ThemedWindowDrawing>
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_BACKGROUND_VIEW_H_

chrome/browser/ui/cocoa/tabs/tab_strip_background_view.mm

@@ -40,33 +40,13 @@
   }
 }
 
-- (void)viewWillMoveToWindow:(NSWindow*)window {
-  if ([self window]) {
-    [[NSNotificationCenter defaultCenter]
-        removeObserver:self
-                  name:NSWindowDidBecomeMainNotification
-                object:[self window]];
-    [[NSNotificationCenter defaultCenter]
-        removeObserver:self
-                  name:NSWindowDidResignMainNotification
-                object:[self window]];
-  }
-  if (window) {
-    [[NSNotificationCenter defaultCenter]
-        addObserver:self
-           selector:@selector(windowFocusDidChange:)
-               name:NSWindowDidBecomeMainNotification
-             object:window];
-    [[NSNotificationCenter defaultCenter]
-        addObserver:self
-           selector:@selector(windowFocusDidChange:)
-               name:NSWindowDidResignMainNotification
-             object:window];
-  }
+// ThemedWindowDrawing implementation.
+
+- (void)windowDidChangeTheme {
+  [self setNeedsDisplay:YES];
 }
 
-- (void)windowFocusDidChange:(NSNotification*)notification {
-  // The theme image may depend on the window's active state.
+- (void)windowDidChangeActive {
   [self setNeedsDisplay:YES];
 }