Use WebKit compositor in ui::Layer

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 5537473ec3f09069f66a80737bd6c2fda455be79..cc29fc1d4562ed7f0e7944cc5d0dd29b8c32cbb2 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -51,6 +51,9 @@
         'use_aura%': '<(use_aura)',
         'use_openssl%': '<(use_openssl)',
 
+        # WebKit compositor for ui
+        'use_webkit_compositor%': 0,
+
         # Compute the architecture that we're building on.
         'conditions': [
           [ 'OS=="win" or OS=="mac"', {
@@ -101,6 +104,7 @@
       'toolkit_views%': '<(toolkit_views)',
       'use_only_pure_views%': '<(use_only_pure_views)',
       'views_compositor%': '<(views_compositor)',
+      'use_webkit_compositor%': '<(use_webkit_compositor)',
       'use_aura%': '<(use_aura)',
       'use_openssl%': '<(use_openssl)',
 
@@ -331,7 +335,7 @@
 
         # Use GPU accelerated cross process image transport by default
         # on TOUCH_UI and linux builds with the Aura window manager
-        ['views_compositor==1 and OS=="linux"', {
+        ['views_compositor==1 and OS=="linux" and use_webkit_compositor!=1', {
           'ui_compositor_image_transport%': 1,
         }, {
           'ui_compositor_image_transport%': 0,
@@ -349,6 +353,7 @@
     'use_only_pure_views%': '<(use_only_pure_views)',
     'views_compositor%': '<(views_compositor)',
     'ui_compositor_image_transport%': '<(ui_compositor_image_transport)',
+    'use_webkit_compositor%': '<(use_webkit_compositor)',
     'use_aura%': '<(use_aura)',
     'use_openssl%': '<(use_openssl)',
     'use_nss%': '<(use_nss)',
@@ -954,6 +959,9 @@
       ['ui_compositor_image_transport==1', {
         'defines': ['UI_COMPOSITOR_IMAGE_TRANSPORT'],
       }],
+      ['use_webkit_compositor==1', {
+        'defines': ['USE_WEBKIT_COMPOSITOR=1'],
+      }],
       ['use_aura==1', {
         'defines': ['USE_AURA=1'],
       }],