Extract mojo_base.gyp from mojo.gyp

This change extract essential part of Mojo, which is needed
to build chrome and its submodules, to mojo_base.gyp.
Other chrome submodules can safely depends on mojo_base.gyp
without worrying about excessive dependencies behind.

Caveat: mojo_service_manager stays on mojo.gyp even though
it is required to build chrome. This change leaves it
as it depends on net.gyp, which has non trivial dependencies.

BUG=397672
TEST=none
R=jamesr@chromium.org, viettrungluu@chromium.org, rockot@chromium.org
TBR=darin@chromium.org

Review URL: https://codereview.chromium.org/422163004

git-svn-id: http://src.chromium.org/svn/trunk/src/build@286627 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

all.gyp

@@ -47,7 +47,7 @@
           'dependencies': [
             '../content/content_shell_and_tests.gyp:content_shell_apk',
             '../mojo/mojo.gyp:mojo_shell_apk',
-            '../mojo/mojo.gyp:mojo_test_apk',
+            '../mojo/mojo_base.gyp:mojo_test_apk',
             '<@(android_app_targets)',
             'android_builder_tests',
             '../android_webview/android_webview.gyp:android_webview_apk',
@@ -90,6 +90,7 @@
             '../media/cast/cast.gyp:*',
             '../media/media.gyp:*',
             '../mojo/mojo.gyp:*',
+            '../mojo/mojo_base.gyp:*',
             '../ppapi/ppapi.gyp:*',
             '../ppapi/ppapi_internal.gyp:*',
             '../ppapi/tools/ppapi_tools.gyp:*',