SurfaceFlinger: recompute visible regions less

This change removes some visible region recomputation that was needed to handle
the SCALING_MODE_FREEZE cropping.  We've changed things to use a window crop
from the WindowManager instead, so this is no longer needed.

Bug: 6299171
Change-Id: I32fbc2b689c985837126d8ba3d9a91e79613ffbf
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 2899db7..7eba89b 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -528,7 +528,6 @@
             mCurrentTransform = transform;
             mCurrentScalingMode = scalingMode;
             mFlinger->invalidateHwcGeometry();
-            recomputeVisibleRegions = true;
         }
 
         uint32_t bufWidth  = mActiveBuffer->getWidth();
@@ -537,7 +536,6 @@
             if (bufWidth != uint32_t(oldActiveBuffer->width) ||
                 bufHeight != uint32_t(oldActiveBuffer->height)) {
                 mFlinger->invalidateHwcGeometry();
-                recomputeVisibleRegions = true;
             }
         }