[Mac] Shut down connections to WindowServer before engaging the sandbox.

The connection is only needed during sandbox warmup to initialize the default
color space. It was formerly needed by scrollbar NSAnimations, but that was
replaced via https://codereview.chromium.org/529103002/.

A similar CL was landed and reverted:
https://chromium.googlesource.com/chromium/src.git/+/53ffdf90f4646dbde8df72007fbdc97f3f0220de

BUG=397642, 306348
TEST=Manually tested on 10.6-10.10.

Review URL: https://codereview.chromium.org/561833006

Cr-Commit-Position: refs/heads/master@{#294382}

content/common/sandbox_mac.mm

@@ -38,6 +38,11 @@ extern "C" {
 #include "ui/base/layout.h"
 #include "ui/gl/gl_surface.h"
 
+extern "C" {
+void CGSSetDenyWindowServerConnections(bool);
+void CGSShutdownServerConnections();
+};
+
 namespace content {
 namespace {
 
@@ -268,8 +273,8 @@ void Sandbox::SandboxWarmup(int sandbox_type) {
         kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host));
 
     // Load in the color profiles we'll need (as a side effect).
-    (void) base::mac::GetSRGBColorSpace();
-    (void) base::mac::GetSystemColorSpace();
+    ignore_result(base::mac::GetSRGBColorSpace());
+    ignore_result(base::mac::GetSystemColorSpace());
 
     // CGColorSpaceCreateSystemDefaultCMYK - 10.6
     base::ScopedCFTypeRef<CGColorSpaceRef> cmyk_colorspace(
@@ -325,6 +330,14 @@ void Sandbox::SandboxWarmup(int sandbox_type) {
     NSColor* color = [NSColor controlTextColor];
     [color colorUsingColorSpaceName:NSCalibratedRGBColorSpace];
   }
+
+  if (sandbox_type == SANDBOX_TYPE_RENDERER) {
+    // Now disconnect from WindowServer, after all objects have been warmed up.
+    // Shutting down the connection requires connecting to WindowServer,
+    // so do this before actually engaging the sandbox.
+    CGSSetDenyWindowServerConnections(true);
+    CGSShutdownServerConnections();
+  }
 }
 
 // static