GitLab

Adds back fling from overview to home screen when
kDragFromShelfToHomeOrOverview is enabled.
With the feature disabled, drag/fling from bottom in overview transitions
to home, and is handled by HomeLauncherGestureHandler. When the feature
is enabled, the gesture is not propagated to HomeLauncherGestureHandler
(as it might have to handle hotseat drag in split view).

This adds handling for the fling in overview to shelf_layout_manager, to
re-enable the gesture - the handling is moved from
HomeLauncherGestureHandler to ShelfLayoutManager to better handle the
case where the hotseat starts off in the hidden state (and fling in
split view can either bring up the hotseat, or go to home screen,
depending on the gesture length) -  handling the gesture in
HomeLauncherGestureHandler means that the drag event would not be
handled as shelf drag event (which brings up the hotseat).

The fling is expected to transition to home if:
*   in overview mode
*   in split view mode with overview, and fling is on the overview
    side (otherwise, the gesture should be handled by
    window_drag_controller_)

BUG=1023910

Change-Id: I2385d195aa06f04d264da926091e6fc4b5f8fe26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935107
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718971}