validate CHROME_SRC setting to avoid confusion

build/android/envsetup.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.
 
 # Sets up environment for building Chromium on Android. Only Android NDK,
 # Revision 6b on Linux or Mac is offically supported.
 #
 # To run this script, the system environment ANDROID_NDK_ROOT must be set
@@ skipping 75 matching lines @@
 
 # Add Android SDK/NDK tools to system path.
 export PATH=$PATH:${ANDROID_NDK_ROOT}
 export PATH=$PATH:${ANDROID_SDK_ROOT}/tools
 export PATH=$PATH:${ANDROID_SDK_ROOT}/platform-tools
 # Must have tools like arm-linux-androideabi-gcc on the path for ninja
 export PATH=$PATH:${ANDROID_TOOLCHAIN}
 
 if [ -z "${CHROME_SRC}" ]; then
   # If $CHROME_SRC was not set, assume current directory is CHROME_SRC.
-  export CHROME_SRC=$(readlink -f .)
+  export CHROME_SRC="${PWD}"
+fi
+
+if [ "${PWD/"${CHROME_SRC}"/}" == "${PWD}" ]; then
+  # If current directory is not in $CHROME_SRC, it might be set for other
+  # source tree. If $CHROME_SRC was set correctly and we are in the correct
+  # directory, "${PWD/"${CHROME_SRC}"/}" will be "".
+  # Otherwise, it will equal to "${PWD}"
+  echo "Warning: Current directory is out of CHROME_SRC, it may not be \
+the one you want."
+  echo "${CHROME_SRC}"
 fi
 
 if [ ! -d "${CHROME_SRC}" ]; then
   echo "CHROME_SRC must be set to the path of Chrome source code." >& 2
   return 1
 fi
 
 # Add Chromium Android development scripts to system path.
 # Must be after CHROME_SRC is set.
 export PATH=$PATH:${CHROME_SRC}/build/android
@@ skipping 37 matching lines @@
 export GYP_DEFINES="${DEFINES}"
 
 # Use the "android" flavor of the Makefile generator for both Linux and OS X.
 export GYP_GENERATORS="make-android"
 
 # Use our All target as the default
 export GYP_GENERATOR_FLAGS="${GYP_GENERATOR_FLAGS} default_target=All"
 
 # We want to use our version of "all" targets.
 export CHROMIUM_GYP_FILE="${CHROME_SRC}/build/all_android.gyp"