build: move libcc patches to electron repo (#14104)

In the GN build, libchromiumcontent is no longer a distinct library, but
merely a container for a set of scripts and patches. Maintaining those
patches in a separate repository is tedious and error-prone, so merge
them into the main repo.

Once this is merged and GN is the default way to build Electron, the
libchromiumcontent repository can be archived.

patches/common/chromium/mas-cgdisplayusesforcetogray.patch

@@ -0,0 +1,34 @@
+From 82d0ef64e22c69c0435608276149977d2811a3f7 Mon Sep 17 00:00:00 2001
+From: Jeremy Apthorp <nornagon@nornagon.net>
+Date: Mon, 6 Aug 2018 10:58:46 -0700
+Subject: fix: [mas] remove usage of CGDisplayUsesForceToGray
+
+---
+ ui/display/mac/screen_mac.mm | 10 ++++++++++
+ 1 file changed, 10 insertions(+)
+
+diff --git a/ui/display/mac/screen_mac.mm b/ui/display/mac/screen_mac.mm
+index 4850c795480e..ec34b25a6fe8 100644
+--- a/ui/display/mac/screen_mac.mm
++++ b/ui/display/mac/screen_mac.mm
+@@ -106,7 +106,17 @@ Display BuildDisplayForScreen(NSScreen* screen) {
+ 
+   display.set_color_depth(NSBitsPerPixelFromDepth([screen depth]));
+   display.set_depth_per_component(NSBitsPerSampleFromDepth([screen depth]));
++#ifdef MAS_BUILD
++  // This is equivalent to the CGDisplayUsesForceToGray() API as at 2018-08-06,
++  // but avoids usage of the private API.
++  CFStringRef app = CFSTR("com.apple.CoreGraphics");
++  CFStringRef key = CFSTR("DisplayUseForcedGray");
++  Boolean key_valid = false;
++  display.set_is_monochrome(
++      CFPreferencesGetAppBooleanValue(key, app, &key_valid));
++#else
+   display.set_is_monochrome(CGDisplayUsesForceToGray());
++#endif
+ 
+   // CGDisplayRotation returns a double. Display::SetRotationAsDegree will
+   // handle the unexpected situations were the angle is not a multiple of 90.
+-- 
+2.17.0
+