Mac: Optimize HistoryOverlayView using layer.

chrome/browser/ui/cocoa/history_overlay_controller.mm

Index: chrome/browser/ui/cocoa/history_overlay_controller.mm
diff --git a/chrome/browser/ui/cocoa/history_overlay_controller.mm b/chrome/browser/ui/cocoa/history_overlay_controller.mm
index 88237a3c6f771d1cc37f5bb940f9d954df5a9270..005913b7fc007e631552059b92c2d165df7ad77b 100644
--- a/chrome/browser/ui/cocoa/history_overlay_controller.mm
+++ b/chrome/browser/ui/cocoa/history_overlay_controller.mm
@@ -5,6 +5,7 @@
 #import "chrome/browser/ui/cocoa/history_overlay_controller.h"
 
 #include "base/logging.h"
+#include "base/mac/scoped_cftyperef.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #include "grit/theme_resources.h"
 #include "ui/base/resource/resource_bundle.h"
@@ -52,6 +53,10 @@ const CGFloat kShieldHeightCompletionAdjust = 10;
   if ((self = [super initWithFrame:frame])) {
     mode_ = mode;
 
+    // A layer-hosting view.
+    [self setLayer:[CALayer layer]];
+    [self setWantsLayer:YES];
+
     // If going backward, the arrow needs to be in the right half of the circle,
     // so offset the X position.
     CGFloat offset = mode_ == kHistoryOverlayModeBack ? kShieldRadius : 0;
@@ -67,11 +72,18 @@ const CGFloat kShieldHeightCompletionAdjust = 10;
   return self;
 }
 
-- (void)drawRect:(NSRect)dirtyRect {
-  NSBezierPath* path = [NSBezierPath bezierPathWithOvalInRect:self.bounds];
-  NSColor* fillColor = [NSColor colorWithCalibratedWhite:0 alpha:shieldAlpha_];
-  [fillColor set];
-  [path fill];
+- (void)setFrameSize:(CGSize)frameSize {
+  [super setFrameSize:frameSize];
+  // Draw an oval.
+  CGFloat radius = std::min(frameSize.width, frameSize.height) / 2.0;

[Robert Sesek, 2015/02/04 00:21:13]

Why min here instead of just always width?

[Andre, 2015/02/04 01:08:55]

height >= width always, so that would work.
Done.
Thinking about this some more, setting corner radius this way is not exactly the
same
as drawing an oval as before. But with the width and height being pretty close
in this
case (140x150), it's very hard to tell the difference.
Do you think it's worth trying to use a CAShapeLayer instead?

+  [[self layer] setCornerRadius:radius];
+}
+
+- (void)setShieldAlpha:(CGFloat)shieldAlpha {
+  shieldAlpha_ = shieldAlpha;
+  base::ScopedCFTypeRef<CGColorRef> fillColor(
+      CGColorCreateGenericGray(0, shieldAlpha));
+  [[self layer] setBackgroundColor:fillColor];
 }
 
 @end
@@ -129,7 +141,6 @@ const CGFloat kShieldHeightCompletionAdjust = 10;
 
   self.view.frame = frame;
   [contentView_ setShieldAlpha:shieldAlpha];
-  [contentView_ setNeedsDisplay:YES];
 }
 
 - (void)showPanelForView:(NSView*)view {