Reverts Chromecast using external V8 snapshot files.

This currently breaks at runtime both cast_shell and cast_shell_apk
and I wasn't able to find an easy fix. I'd like to unblock our other development in the meantime.

Half-revert of https://codereview.chromium.org/1019123002/

TBR=jochen@chromium.org
R=rmcilroy@chromium.org,lcwu@chromium.org
BUG=421063

Review URL: https://codereview.chromium.org/1073583004

Cr-Commit-Position: refs/heads/master@{#324376}

build/common.gypi

@@ -1022,8 +1022,8 @@
           'optimize_jni_generation%': 0,
         }],
 
-        # TODO(rmcilroy): Remove ios check. http://crbug.com/421063.
-        ['OS!="ios"', {
+        # TODO(rmcilroy): Remove ios/chromecast checks. http://crbug.com/421063.
+        ['OS!="ios" and chromecast==0', {
           'v8_use_external_startup_data%': 1,
         }, {
           'v8_use_external_startup_data%': 0,

chromecast/chromecast.gyp

@@ -354,14 +354,11 @@
           'type': 'none',
           'dependencies': [
             '../third_party/icu/icu.gyp:icudata',
-            '../v8/tools/gyp/v8.gyp:v8_external_snapshot',
           ],
           'copies': [{
             'destination': '<(PRODUCT_DIR)/assets',
             'files': [
               '<(PRODUCT_DIR)/icudtl.dat',
-              '<(PRODUCT_DIR)/natives_blob.bin',
-              '<(PRODUCT_DIR)/snapshot_blob.bin',
             ],
           }],
         },