Remove CHROME_V8 #define and related javascript_engine gyp variable.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index a64ab3758b89dce365e87ec33c771897d1100b83..821f94cecb05a2c1f29b0c5a04225cf00ae80fe8 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -37,12 +37,12 @@
 
           # Disable webui dialog replacements for native dialogs by default.
           # TODO(flackr): Change this to a runtime flag triggered by
-          #     --pure-views so that these dialogs can be easily tested. 
+          #     --pure-views so that these dialogs can be easily tested.
           'webui_dialogs%': 0,
 
           # Whether the compositor is enabled on views.
           'views_compositor%': 0,
-          
+
           # Whether or not we are building with the Aura window manager.
           'use_aura%': 0,
         },
@@ -85,7 +85,7 @@
           ['touchui==1', {
             'webui_dialogs%': 1,
           }],
-          
+
           # Use the views compositor when using the Aura window manager.
           ['use_aura==1', {
             'views_compositor%': 1,
@@ -269,7 +269,7 @@
         }, {
           'file_manager_extension%': 0,
         }],
-        
+
         # Enable WebUI TaskManager only on Chrome OS and Touch UI.
         ['chromeos==1 or touchui==1', {
           'webui_task_manager%': 1,
@@ -369,10 +369,6 @@
     # Currently ignored on Windows.
     'coverage%': 0,
 
-    # Overridable specification for potential use of alternative
-    # JavaScript engines.
-    'javascript_engine%': 'v8',
-
     # Although base/allocator lets you select a heap library via an
     # environment variable, the libcmt shim it uses sometimes gets in
     # the way.  To disable it entirely, and switch to normal msvcrt, do e.g.