[Android] Generate scripts at build time to run android tests.

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index f5e797b61fe5ea05cc3abeccf93be9587a92859d..6f34f1633173646dc5d2c204500b81ef57c93cb5 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -1668,6 +1668,7 @@
           ],
           'variables': {
             'test_suite_name': 'media_unittests',
+            'isolate_file': 'media_unittests.isolate',
           },
           'includes': ['../build/apk_test.gypi'],
         },
@@ -1681,6 +1682,7 @@
           ],
           'variables': {
             'test_suite_name': 'media_perftests',
+            'isolate_file': 'media_perftests.isolate',
           },
           'includes': ['../build/apk_test.gypi'],
         },