[Mac] Update tab audio icon to Material Design and tweak close box color.

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

Index: chrome/browser/ui/cocoa/tabs/tab_view.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_view.mm b/chrome/browser/ui/cocoa/tabs/tab_view.mm
index 3e884a9cc7d9dd8d851c2696eb03562651702bcf..605432eb76ca6b498aeefe8c6f12ed955b2280da 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_view.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_view.mm
@@ -53,6 +53,11 @@ const CGFloat kRapidCloseDist = 2.5;
 + (void)drawTabRightEdgeImage;
 @end
 
+@interface TabController(Private)
+// The TabView's close button.
+- (HoverCloseButton*)closeButton;
+@end
+
 namespace {
 
 NSImage* imageForResourceID(int resource_id) {
@@ -590,6 +595,10 @@ CGFloat LineWidthFromContext(CGContextRef context) {
   [self setNeedsDisplayInRect:[titleView_ frame]];
 }
 
+- (SkColor)closeButtonColor {
+  return [[controller_ closeButton] iconColor];
+}
+
 - (void)setState:(NSCellStateValue)state {
   if (state_ == state)
     return;