Support gesture margin for default Scroll

[dshiroma]

• Applying Scroll margin property to all RPC calls to scroll.

Example usage now works as expected:

ad.ui(res='com.android.chrome:id/compositor_view_holder')
    .scroll(margin=100)  # <--- wouldn't have done anything before
    .down(percent=70, speed=700)

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This change is 

[ko1in1u]

Please help to build and update apk here as well, thank you.

[dshiroma]

Added .apk file.

[eric100lin]

Reviewed 2 of 2 files at r1, 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @dshiroma and @ko1in1u)

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snippet_uiautomator/android/app/src/main/java/com/google/android/mobly/snippet/uiautomator/UiObject2Snippet.java line 313 at r3 (raw file):

      throws SelectorException {
    Direction direction = Direction.valueOf(directionStr);
    UiObject2 uiObject2 = selector.toUiObject2();

nit: it would be nice to declare these variables as final

Suggestion:

    final Direction direction = Direction.valueOf(directionStr);

    final UiObject2 uiObject2 = selector.toUiObject2();

[dshiroma]

Reviewed 2 of 2 files at r1, 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @dshiroma and @ko1in1u)

snippet_uiautomator/android/app/src/main/java/com/google/android/mobly/snippet/uiautomator/UiObject2Snippet.java line 313 at r3 (raw file):

      throws SelectorException {
    Direction direction = Direction.valueOf(directionStr);
    UiObject2 uiObject2 = selector.toUiObject2();

nit: it would be nice to declare these variables as final

Suggestion:

    final Direction direction = Direction.valueOf(directionStr);

    final UiObject2 uiObject2 = selector.toUiObject2();

Done.