Pass -Oz flag to Clang when targeting Android.

build/common.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 3723 matching lines @@
               }],
               ['OS=="android" and target_arch!="mipsel" and target_arch!="mips64el"', {
                 # TODO(jdduke) Re-enable on mips after resolving linking
                 # issues with libc++ (crbug.com/456380).
                 'ldflags': [
                   # Warn in case of text relocations.
                   '-Wl,--warn-shared-textrel',
                 ],
               }],
               ['OS=="android"', {
-                'variables': {
-                  'release_optimize%': 's',
-                },
+                'conditions': [
+                  ['clang==1', {
+                    'variables': {
+                      'release_optimize%': 'z',

[pasko, 2015/04/30 15:48:48]

counter-intuitively there is another file to be tweaked:
build/android/increase_size_for_speed.gypi

+                    },
+                  }, {
+                    'variables': {
+                      'release_optimize%': 's',
+                    },
+                  }],
+                ],
               }],
               ['profiling==1', {
                 'cflags': [
                   '-fno-omit-frame-pointer',
                   '-g',
                 ],
                 'conditions' : [
                   ['profiling_full_stack_frames==1', {
                     'cflags': [
                       '-fno-inline',
@@ skipping 2343 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }