Avoid crashes and performance problems with large cells (relanded). b=444864,444260,449111 r=josh sr=roc

widget/src/cocoa/nsNativeThemeCocoa.mm

@@ -198,6 +198,15 @@ nsNativeThemeCocoa::DrawCheckbox(CGContextRef cgContext, ThemeButtonKind inKind,
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
+// Limit on the area of destRect (in pixels^2) in DrawCellWithScaling(),
+// above which we don't do any scaling.  This is to avoid crashes in
+// [NSGraphicsContext graphicsContextWithGraphicsPort:flipped:] and
+// CGContextDrawImage(), and also to avoid very poor drawing performance in
+// CGContextDrawImage() (particularly if xscale or yscale is less than but
+// near 1 -- e.g. 0.9).  This value was determined by trial and error, on
+// OS X 10.4.11 and 10.5.4, and on systems with different amounts of RAM.
+#define CELL_SCALING_MAX_AREA 500000
+
 /*
  * Draw the given NSCell into the given cgContext.
  *
@@ -265,6 +274,10 @@ nsNativeThemeCocoa::DrawCellWithScaling(NSCell *cell,
   if (doSaveCTM)
     savedCTM = CGContextGetCTM(cgContext);
 
+  // Fall back to no scaling if the area of our cell (in pixels^2) is too large.
+  if (drawRect.size.width * drawRect.size.height > CELL_SCALING_MAX_AREA)
+    xscale = yscale = 1.0f;
+
   if (xscale == 1.0f && yscale == 1.0f) {
     // Inflate the rect Gecko gave us by the margin for the control.
     InflateControlRect(&drawRect, controlSize, marginSet);
@@ -273,6 +286,8 @@ nsNativeThemeCocoa::DrawCellWithScaling(NSCell *cell,
     savedContext = [NSGraphicsContext currentContext];
     [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:cgContext flipped:YES]];
 
+    // [NSView focusView] may return nil here, but
+    // [NSCell drawWithFrame:inView:] can deal with that.
     [cell drawWithFrame:drawRect inView:[NSView focusView]];
   }
   else {
@@ -300,6 +315,8 @@ nsNativeThemeCocoa::DrawCellWithScaling(NSCell *cell,
     savedContext = [NSGraphicsContext currentContext];
     [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:ctx flipped:YES]];
 
+    // [NSView focusView] may return nil here, but
+    // [NSCell drawWithFrame:inView:] can deal with that.
     [cell drawWithFrame:tmpRect inView:[NSView focusView]];
 
     [NSGraphicsContext setCurrentContext:savedContext];