Use the NDK that has been checked into android_tools.

build/android/envsetup_functions.sh

 #!/bin/bash
 
 # 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.
 
 # Defines functions for envsetup.sh which sets up environment for building
 # Chromium on Android.  The build can be either use the Android NDK/SDK or
 # android source tree.  Each has a unique init function which calls functions
 # prefixed with "common_" that is common for both environment setups.
@@ skipping 128 matching lines @@
 # ANDROID_SDK_ROOT only needs to be set to override the default SDK which is in
 # the tree under $ROOT/src/third_party/android_tools/sdk.
 # TODO(navabi): Add NDK to $ROOT/src/third_party/android_tools/ndk.
 # To build Chromium for Android with NDK/SDK follow the steps below:
 #  > export ANDROID_NDK_ROOT=<android ndk root>
 #  > export ANDROID_SDK_ROOT=<android sdk root> # to override the default sdk
 #  > . build/android/envsetup.sh --sdk
 #  > make
 ################################################################################
 sdk_build_init() {
+  # If ANDROID_NDK_ROOT is set when envsetup is run, use the ndk pointed to by
+  # the environment variable.  Otherwise, use the default ndk from the tree.
   if [ ! -d "${ANDROID_NDK_ROOT}" ]; then
-    echo "ANDROID_NDK_ROOT must be set to the path of Android NDK." >& 2
-    echo "which could be installed by" >& 2
-    echo "<chromium_tree>/src/build/install-build-deps-android-sdk.sh" >& 2
-    return 1
+    export ANDROID_NDK_ROOT="${CHROME_SRC}/third_party/android_tools/ndk/"
   fi
 
   # If ANDROID_SDK_ROOT is set when envsetup is run, use the sdk pointed to by
   # the environment variable.  Otherwise, use the default sdk from the tree.
   if [ ! -d "${ANDROID_SDK_ROOT}" ]; then
     export ANDROID_SDK_ROOT="${CHROME_SRC}/third_party/android_tools/sdk/"
   fi
 
   # Makes sure ANDROID_BUILD_TOP is unset if build has option --sdk
   unset ANDROID_BUILD_TOP
@@ skipping 113 matching lines @@
 
   export GYP_GENERATORS="android"
 
   export GYP_GENERATOR_FLAGS="${GYP_GENERATOR_FLAGS} default_target=All"
   export GYP_GENERATOR_FLAGS="${GYP_GENERATOR_FLAGS} limit_to_target_all=1"
   export GYP_GENERATOR_FLAGS="${GYP_GENERATOR_FLAGS} auto_regeneration=0"
 
   # TODO(torne): This isn't upstream yet. Upstream it or remove this setting.
   export CHROMIUM_GYP_FILE="${CHROME_SRC}/build/all_android_webview.gyp"
 }