cc: Do not create separate tilings for almost equal scale factors.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index f8aa213a92596eef4bcf8a843933d4c1d6f10da2..747d4d7c9ae14222607420a4f4dfacf5682e267f 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -48,6 +48,12 @@ const int kMinHeightForGpuRasteredTile = 256;
 // of using the same tile size.
 const int kTileRoundUp = 64;
 
+// The precision value for rounding floating points values of scale factors.
+// With this scale factors will be having 3 digits fractional part, which will
+// make almost equal (having smaller difference by some magnitude of floating
+// point epsilon) scale factors to be considered as same.
+const int kScalePrecision = 4;
+
 }  // namespace
 
 namespace cc {
@@ -942,7 +948,10 @@ void PictureLayerImpl::RecalculateRasterScales() {
   raster_device_scale_ = ideal_device_scale_;
   raster_page_scale_ = ideal_page_scale_;
   raster_source_scale_ = ideal_source_scale_;
-  raster_contents_scale_ = ideal_contents_scale_;
+  // Get fixed precision scale to avoid creating extra tilings for scales
+  // which are almost equal.
+  raster_contents_scale_ =
+      MathUtil::RoundToFixedPrecision(ideal_contents_scale_, kScalePrecision);
 
   // If we're not animating, or leaving an animation, and the
   // ideal_source_scale_ changes, then things are unpredictable, and we fix