[Android] Switch chromium.gpu bots to mb.

build/android/buildbot/bb_host_steps.py

Index: build/android/buildbot/bb_host_steps.py
diff --git a/build/android/buildbot/bb_host_steps.py b/build/android/buildbot/bb_host_steps.py
index 11f5032aa8665879821d0d0b2416066ffc892ce2..c0b167a668ff522e245a036491c4bacef6976661 100755
--- a/build/android/buildbot/bb_host_steps.py
+++ b/build/android/buildbot/bb_host_steps.py
@@ -50,8 +50,24 @@ def RunHooks(build_type):
   RunCmd(['gclient', 'runhooks'], halt_on_failure=True)
 
 
+def GenerateBuildFiles(options):
+  cmd = [SrcPath('tools', 'mb', 'mb.py'),
+         'gen',
+         '-m', options.build_properties['mastername'],
+         '-b', options.build_properties['buildername'],
+         '//out/%s' % options.target]
+  bb_annotations.PrintNamedStep('generate_build_files')
+  RunCmd(cmd, halt_on_failure=True)
+
+
 def Compile(options):
-  RunHooks(options.target)
+  if options.run_mb:
+    os.environ['GYP_CHROMIUM_NO_ACTION'] = '1'
+    RunHooks(options.target)
+    GenerateBuildFiles(options)
+  else:
+    RunHooks(options.target)
+
   cmd = [os.path.join(SLAVE_SCRIPTS_DIR, 'compile.py'),
          '--build-tool=ninja',
          '--compiler=goma',
@@ -111,6 +127,8 @@ def GetHostStepsOptParser():
   parser.add_option('--extra_src', default='',
                     help='Path to extra source file. If this is supplied, '
                     'bisect script will use it to override default behavior.')
+  parser.add_option('--run-mb', action='store_true',
+                    help='Use mb to generate build files.')
 
   return parser