cc: Prevent small scale factors (below 1) from being used or saved as the layer's rasterScale.

cc/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "cc/layer_tree_host_common.h"
 
 #include "cc/layer.h"
 #include "cc/layer_impl.h"
@@ skipping 345 matching lines @@
     float rasterScale = layer->rasterScale();
     if (!rasterScale) {
         rasterScale = 1;
 
         if (!animatingTransformToScreen && layer->automaticallyComputeRasterScale()) {
             gfx::Vector2dF transformScale = MathUtil::computeTransform2dScaleComponents(combinedTransform);
             float combinedScale = std::max(transformScale.x(), transformScale.y());
             rasterScale = combinedScale / deviceScaleFactor;
             if (!layer->boundsContainPageScale())
                 rasterScale /= pageScaleFactor;
-            layer->setRasterScale(rasterScale);
+            // Prevent scale factors below 1 from being used or saved.
+            if (rasterScale < 1)
+                rasterScale = 1;
+            else
+                layer->setRasterScale(rasterScale);
         }
     }
 
     float contentsScale = rasterScale * deviceScaleFactor;
     if (!layer->boundsContainPageScale())
         contentsScale *= pageScaleFactor;
     layer->setContentsScale(contentsScale);
 
     Layer* maskLayer = layer->maskLayer();
     if (maskLayer)
@@ skipping 547 matching lines @@
 
         foundLayer = currentLayer;
         break;
     }
 
     // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
     return foundLayer;
 }
 
 }  // namespace cc