[Cronet] Use is_official_build=true for Cronet builds.

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index a17e5f4ef8b38dbd515c5b7996ea7589a297ce38..ff6a9e57b4e32521c06550a15a96dbde3d67c4a4 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -735,27 +735,27 @@
     ],
 
     'android_cronet_release_bot_minimal_symbols_arm64': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'arm64',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'arm64',
     ],
 
     'android_cronet_release_bot_minimal_symbols_armv6': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'armv6',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'armv6',
     ],
 
     'android_cronet_release_bot_minimal_symbols_arm_no_neon': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'arm_no_neon',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'arm_no_neon',
     ],
 
     'android_cronet_release_bot_minimal_symbols_arm_no_neon_clang_asan': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'arm_no_neon', 'clang', 'asan',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'arm_no_neon', 'clang', 'asan',
     ],
 
     'android_cronet_release_bot_minimal_symbols_mipsel': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'mipsel',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'mipsel',
     ],
 
     'android_cronet_release_bot_minimal_symbols_x86': [
-      'android', 'cronet', 'release_bot', 'minimal_symbols', 'x86',
+      'android', 'cronet', 'official_optimize', 'release_bot', 'minimal_symbols', 'x86',
     ],
 
     'android_cronet_release_trybot_arm_no_neon': [