FlingTracker can divide by zero and hang StatusBar in an infinite loop

if 2 events have the same timestamp then FlingTracker in PanelView will divide
by zero causing NaNs. the bug is usually triggered by rapid StatusBar up/down
dragging activity and updateCarrierLabelVisibility can then loop indefinitely
looking at NaNs. the user visible symptom is that StatusBar refuses to pull
down and is burning cpu time.

Signed-off-by: Michael Bestas <mikeioannina@gmail.com>

Change-Id: I0791c6bea953bf03346185fc6aaf44aaea79aace
Remove opaque check in GLRenderer when preparing dirty region.

Since preserved swap is enabled, we need to clear the color buffer
when the scissor rect is prepared for a new process. This prevents
garbage to be present from the previous process in the color buffer.

CRs-Fixed: 391492, 403067, 405916

Change-Id: I1f72a3dee2f5d58a984f4cd367c9f7bf08ab9d6a

Conflicts:

	libs/hwui/OpenGLRenderer.cpp

[PATCH] Remove opaque check in preparing dirty region

Since preserved swap is enabled, we need to clear the color buffer
when the scissor rect is prepared for a new rocess. This prevents
garbage to be present from the previous process in the color buffer.

(cherry picked from commit 2b5e584e2615852b68a69bb529c6926190246b64)

Change-Id: I92a4fa35e0746f12fcd736e21fd30d9c4b644a8a
CRs-Fixed: 391492, 403067, 405916

Conflicts:

	libs/hwui/OpenGLRenderer.cpp

Enable scissor when preparing dirty rect that is opaque

Now enabling scissor before setting it in the opaque case, previously was not doing so.

Change-Id: I1ea904cf01603096e423556090564291ab712d36
CRs-Fixed: 465346
Depends-on: 278453