[Mac] Allow vibrancy & transparency on WebContentsView

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
diff --git a/content/browser/web_contents/web_contents_view_mac.mm b/content/browser/web_contents/web_contents_view_mac.mm
index 27989c3951ffce334f0a2f48c2db99b67f3695df..1436d3957828439050fc4f38671f5f8cb8d085a8 100644
--- a/content/browser/web_contents/web_contents_view_mac.mm
+++ b/content/browser/web_contents/web_contents_view_mac.mm
@@ -423,6 +423,14 @@ void WebContentsViewMac::CloseTab() {
   [super dealloc];
 }
 
+- (BOOL)allowsVibrancy {
+  // Returning YES will allow rendering this view with vibrancy effect if it is
+  // incorporated into a view hierarchy that uses vibrancy, it will have no
+  // effect otherwise.
+  // For details see Apple documentation on NSView and NSVisualEffectView.
+  return YES;
+}
+
 // Registers for the view for the appropriate drag types.
 - (void)registerDragTypes {
   NSArray* types = [NSArray arrayWithObjects:
@@ -479,6 +487,13 @@ void WebContentsViewMac::CloseTab() {
   return mouseDownCanMoveWindow_;
 }
 
+- (void)setOpaque:(BOOL)opaque {
+  RenderWidgetHostViewMac* view = static_cast<RenderWidgetHostViewMac*>(
+      webContentsView_->web_contents()->GetRenderWidgetHostView());
+  DCHECK(view);
+  [view->cocoa_view() setOpaque:opaque];
+}
+
 - (void)pasteboard:(NSPasteboard*)sender provideDataForType:(NSString*)type {
   [dragSource_ lazyWriteToPasteboard:sender
                              forType:type];