[Android] Allow more support for experimentation with SDK.

build/android/envsetup_functions.sh

Index: build/android/envsetup_functions.sh
diff --git a/build/android/envsetup_functions.sh b/build/android/envsetup_functions.sh
index 9554bc9f299c6db6bac703589c5f200a4b649747..f7cf4a1b2c10426c717e880e074b7b3cf120cf1e 100755
--- a/build/android/envsetup_functions.sh
+++ b/build/android/envsetup_functions.sh
@@ -218,23 +218,24 @@ process_options() {
 #  > make
 ################################################################################
 sdk_build_init() {
-  export ANDROID_SDK_VERSION=18
-  export ANDROID_SDK_BUILD_TOOLS_VERSION=18.0.1
 
-  # 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.
+  # Allow the caller to override a few environment variables. If any of them is
+  # unset, we default to a sane value that's known to work. This allows for
+  # experimentation with a custom SDK.
   if [[ -z "${ANDROID_NDK_ROOT}" || ! -d "${ANDROID_NDK_ROOT}" ]]; then

[Isaac (away), 2013/08/13 02:19:54]

How about we remove the -d check (checks the variable points to a valid
directory)?  We could trust the caller to have a proper environment.

     export ANDROID_NDK_ROOT="${CHROME_SRC}/third_party/android_tools/ndk/"
   fi
-
-  # If ANDROID_SDK_ROOT is set when envsetup is run, and if it has the
-  # right SDK-compatible directory layout, use the sdk pointed to by the
-  # environment variable.  Otherwise, use the default sdk from the tree.
+  if [[ -z "${ANDROID_SDK_VERSION}" ]]; then

[Isaac (away), 2013/08/13 02:19:54]

technically quotes aren't needed in a double bracket test, but it's fine, and
matches the style of the file.

+    export ANDROID_SDK_VERSION=18
+  fi
   local sdk_suffix=platforms/android-${ANDROID_SDK_VERSION}
   if [[ -z "${ANDROID_SDK_ROOT}" || \
        ! -d "${ANDROID_SDK_ROOT}/${sdk_suffix}" ]]; then

[Isaac (away), 2013/08/13 02:19:54]

ditto on -d here

[Yaron, 2013/08/13 02:24:46]

I actually like this. It helped me catch an issue where my custom SDK had a
slightly different folder structure.

     export ANDROID_SDK_ROOT="${CHROME_SRC}/third_party/android_tools/sdk/"
   fi
+  if [[ -z "${ANDROID_SDK_BUILD_TOOLS_VERSION}" ]]; then
+    export ANDROID_SDK_BUILD_TOOLS_VERSION=18.0.1
+  fi
 
   unset ANDROID_BUILD_TOP