android envsetup: If ANDROID_SDK_ROOT is set, honor it unconditionally.

android envsetup: If ANDROID_SDK_ROOT is set, honor it unconditionally.

If this patch breaks your build, try running `unset ANDROID_SDK_ROOT`.

Before this patch, envsetup checked if
${ANDROID_SDK_ROOT}/platforms/android-${ANDROID_SDK_VERSION} existed and fell
back to the sdk in chromium's third_party if that wasn't the case.
Since most people don't set ANDROID_SDK_ROOT and the ones who do will be
able to realize that they're using an SDK that doesn't have the right toolchain
version, this seems save to do. (The motivation is that I want to move
ANDROID_SDK_VERSION out of envsetup and into common.gypi.)
This reverts part of https://chromiumcodereview.appspot.com/10920094

BUG=330631
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248483

[Torne, 2014-02-03 10:42:34]

lgtm

[Nico, 2014-02-03 11:25:32]

The CQ bit was checked by thakis@chromium.org

[commit-bot: I haz the power, 2014-02-03 11:25:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/152173002/1

[commit-bot: I haz the power, 2014-02-03 14:02:38]

Change committed as 248483

[commit-bot: I haz the power, 2014-02-03 14:02:40]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-02-03 14:02:44]

CQ bit was unchecked on CL. Ignoring.