Android: Update docs to be more explicit

Explicitly call out what flag needs to be changed if a new SDK location
is desired for Android Studio. This way the change is explicit and we do
not fall into the trap of recommending the default location Android
Studio suggests, which unfortunately happens to just be the last-used
sdk location.

We now recommend emulators so no need for the emulator warning section.

~/Android/Sdk is now the default, so removing blurb.

Bug: 620034
Change-Id: I371f8576cdcb190e31cbf8ce537800db71cf04de
Reviewed-on: https://chromium-review.googlesource.com/1138175Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575266}

docs/android_studio.md

@@ -11,10 +11,6 @@ Make sure you have followed
 build/android/gradle/generate_gradle.py --output-directory out/Debug
 ```
 
-Use the flag `--sdk AndroidStudioDefault` to create and use a custom sdk
-directory and avoid issues with `gclient sync` and to use emulators. This will
-become the default soon.
-
 ```shell
 build/android/gradle/generate_gradle.py --output-directory out/Debug --sdk AndroidStudioDefault
 ```
@@ -26,17 +22,14 @@ To import the project:
 * Use "Import Project", and select the directory containing the generated
   project, e.g. `out/Debug/gradle`.
 
-For first-time Android Studio users:
-* Only run the setup wizard if you are planning to use emulators.
-    * The wizard will force you to download SDK components that are only needed
-      for emulation.
-    * To skip it, select "Cancel" when it comes up.
-
 See [android_test_instructions.md](android_test_instructions.md#Using-Emulators)
 for more information about building and running emulators.
 
 If you're asked to use Studio's Android SDK:
-* No. (Always use your project's SDK configured by generate_gradle.py)
+* No.
+    * Selecting No ensures that the SDK used by Android Studio is the same as
+      the one set by `generate_gradle.py`. If you want a different SDK pass
+      `--sdk` to `generate_gradle.py`.
 
 If you're asked to use Studio's Gradle wrapper:
 * Yes.