Bug 1291457 - Remove shadow invalidation code. r=spohl

Invalidating a window's shadow is really slow and leads to flickering. Now that
arrow panels don't change their contents during the panel opening animation any
more, their shape stays the same after the first paint, so we don't need the
shadow invalidation functionality for them any more. And as far as I know, we
don't use transparent popups with changing shapes anywhere else.
The system still computes the shadow for the first paint of the window (which
happens during the orderFront call), and it updates the shadow whenever the
window resizes. But not when its size stays the same and only what we draw in
the content is updated.

MozReview-Commit-ID: 138PjbrSFrc

widget/cocoa/nsChildView.mm

@@ -3767,12 +3767,6 @@ - (void)drawRect:(NSRect)aRect
 {
   CGContextRef cgContext = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
   [self drawRect:aRect inContext:cgContext];
-
-  // If we're a transparent window and our contents have changed, we need
-  // to make sure the shadow is updated to the new contents.
-  if ([[self window] isKindOfClass:[BaseWindow class]]) {
-    [(BaseWindow*)[self window] deferredInvalidateShadow];
-  }
 }
 
 - (void)drawRect:(NSRect)aRect inContext:(CGContextRef)aContext

widget/cocoa/nsCocoaWindow.h

@@ -41,9 +41,6 @@ typedef struct _nsCocoaWindowList {
   NSColor* mActiveTitlebarColor;
   NSColor* mInactiveTitlebarColor;
 
-  // Shadow
-  BOOL mScheduledShadowInvalidation;
-
   // Invalidation disabling
   BOOL mDisabledNeedsDisplay;
 
@@ -69,8 +66,6 @@ typedef struct _nsCocoaWindowList {
 - (void)setTitlebarColor:(NSColor*)aColor forActiveWindow:(BOOL)aActive;
 - (NSColor*)titlebarColorForActiveWindow:(BOOL)aActive;
 
-- (void)deferredInvalidateShadow;
-- (void)invalidateShadow;
 - (float)getDPI;
 
 - (void)mouseEntered:(NSEvent*)aEvent;

widget/cocoa/nsCocoaWindow.mm

@@ -3000,7 +3000,6 @@ - (id)initWithContentRect:(NSRect)aContentRect styleMask:(NSUInteger)aStyle back
   mState = nil;
   mActiveTitlebarColor = nil;
   mInactiveTitlebarColor = nil;
-  mScheduledShadowInvalidation = NO;
   mDisabledNeedsDisplay = NO;
   mDPI = GetDPI(self);
   mTrackingArea = nil;
@@ -3150,21 +3149,6 @@ - (NSColor*)titlebarColorForActiveWindow:(BOOL)aActive
   return aActive ? mActiveTitlebarColor : mInactiveTitlebarColor;
 }
 
-- (void)deferredInvalidateShadow
-{
-  if (mScheduledShadowInvalidation || [self isOpaque] || ![self hasShadow])
-    return;
-
-  [self performSelector:@selector(invalidateShadow) withObject:nil afterDelay:0];
-  mScheduledShadowInvalidation = YES;
-}
-
-- (void)invalidateShadow
-{
-  [super invalidateShadow];
-  mScheduledShadowInvalidation = NO;
-}
-
 - (float)getDPI
 {
   return mDPI;