mac: attempt to fix a startup perf regression after r174653

chrome/browser/ui/cocoa/image_button_cell.mm

Index: chrome/browser/ui/cocoa/image_button_cell.mm
diff --git a/chrome/browser/ui/cocoa/image_button_cell.mm b/chrome/browser/ui/cocoa/image_button_cell.mm
index 3223db8b3b85b97bf7aac80600ab01ccac39a69b..5457908483efabc93baa352b31639fa42b754860 100644
--- a/chrome/browser/ui/cocoa/image_button_cell.mm
+++ b/chrome/browser/ui/cocoa/image_button_cell.mm
@@ -58,20 +58,34 @@ const CGFloat kImageNoFocusAlpha = 0.65;
   [self setShowsBorderOnlyWhileMouseInside:YES];
 }
 
+- (NSImage*)imageForState:(image_button_cell::ButtonState)state
+                     view:(NSView*)controlView{
+  if (image_[state].imageId)
+    return [self imageForID:image_[state].imageId controlView:controlView];
+  return image_[state].image;
+}
+
 - (void)drawWithFrame:(NSRect)cellFrame inView:(NSView*)controlView {
+  image_button_cell::ButtonState state = [self currentButtonState];
   BOOL windowHasFocus = [[controlView window] isMainWindow] ||
                         [[controlView window] isKeyWindow];
   CGFloat alpha = windowHasFocus ? 1.0 : kImageNoFocusAlpha;
-  NSImage* image = image_[[self currentButtonState]];
+  NSImage* image = [self imageForState:state view:controlView];
 
   if (!windowHasFocus) {
+    NSImage* defaultImage = [self
+      imageForState:image_button_cell::kDefaultStateBackground
+               view:controlView];
+    NSImage* hoverImage = [self
+      imageForState:image_button_cell::kHoverStateBackground
+               view:controlView];
     if ([self currentButtonState] == image_button_cell::kDefaultState &&
-        image_[image_button_cell::kDefaultStateBackground]) {
-      image = image_[image_button_cell::kDefaultStateBackground];
+        defaultImage) {
+      image = defaultImage;
       alpha = 1.0;
     } else if ([self currentButtonState] == image_button_cell::kHoverState &&
-        image_[image_button_cell::kHoverStateBackground]) {
-      image = image_[image_button_cell::kHoverStateBackground];
+        hoverImage) {
+      image = hoverImage;
       alpha = 1.0;
     }
   }
@@ -110,9 +124,12 @@ const CGFloat kImageNoFocusAlpha = 0.65;
 
 - (void)setImageID:(NSInteger)imageID
     forButtonState:(image_button_cell::ButtonState)state {
-  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-  NSImage* image = imageID ? rb.GetNativeImageNamed(imageID).ToNSImage() : nil;
-  [self setImage:image forButtonState:state];
+  DCHECK_GE(state, 0);
+  DCHECK_LT(state, image_button_cell::kButtonStateCount);
+
+  image_[state].image.reset();
+  image_[state].imageId = imageID;
+  [[self controlView] setNeedsDisplay:YES];
 }
 
 // Sets the image for the given button state using an image.
@@ -120,7 +137,9 @@ const CGFloat kImageNoFocusAlpha = 0.65;
   forButtonState:(image_button_cell::ButtonState)state {
   DCHECK_GE(state, 0);
   DCHECK_LT(state, image_button_cell::kButtonStateCount);
-  image_[state].reset([image retain]);
+
+  image_[state].image.reset([image retain]);
+  image_[state].imageId = 0;
   [[self controlView] setNeedsDisplay:YES];
 }
 
@@ -132,14 +151,17 @@ const CGFloat kImageNoFocusAlpha = 0.65;
 }
 
 - (image_button_cell::ButtonState)currentButtonState {
-  if (![self isEnabled] && image_[image_button_cell::kDisabledState])
+  bool (^has)(image_button_cell::ButtonState) =
+      ^(image_button_cell::ButtonState state) {
+          return image_[state].image || image_[state].imageId;
+      };
+  if (![self isEnabled] && has(image_button_cell::kDisabledState))
     return image_button_cell::kDisabledState;
-  else if ([self isHighlighted] && image_[image_button_cell::kPressedState])
+  if ([self isHighlighted] && has(image_button_cell::kPressedState))
     return image_button_cell::kPressedState;
-  else if ([self isMouseInside] && image_[image_button_cell::kHoverState])
+  if ([self isMouseInside] && has(image_button_cell::kHoverState))
     return image_button_cell::kHoverState;
-  else
-    return image_button_cell::kDefaultState;
+  return image_button_cell::kDefaultState;
 }
 
 - (NSImage*)imageForID:(NSInteger)imageID