Round the scroll offset synced back to main instead of flooring.

cc/trees/layer_tree_host_unittest_scroll.cc

 // Copyright 2012 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 "cc/trees/layer_tree_host.h"
 
 #include "base/location.h"
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 444 matching lines @@
       case 0:
         EXPECT_VECTOR_EQ(
             gfx::Vector2d(0, 0),
             ScrollTreeForLayer(scroll_layer)
                 ->GetScrollOffsetBaseForTesting(scroll_layer->id()));
         EXPECT_VECTOR_EQ(gfx::Vector2d(0, 0), ScrollDelta(scroll_layer));
         PostSetNeedsCommitToMainThread();
         break;
       case 1:
         EXPECT_VECTOR_EQ(
-            gfx::ToFlooredVector2d(scroll_amount_),
+            gfx::ToRoundedVector2d(scroll_amount_),
             ScrollTreeForLayer(scroll_layer)
                 ->GetScrollOffsetBaseForTesting(scroll_layer->id()));
-        EXPECT_VECTOR_EQ(gfx::Vector2dF(fmod(scroll_amount_.x(), 1.0f), 0.0f),
-                         ScrollDelta(scroll_layer));
+        EXPECT_VECTOR_EQ(
+            scroll_amount_ - gfx::ToRoundedVector2d(scroll_amount_),
+            ScrollDelta(scroll_layer));
         PostSetNeedsCommitToMainThread();
         break;
       case 2:
         EXPECT_VECTOR_EQ(
-            gfx::ToFlooredVector2d(scroll_amount_ + scroll_amount_),
+            gfx::ToRoundedVector2d(scroll_amount_ + scroll_amount_),
             ScrollTreeForLayer(scroll_layer)
                 ->GetScrollOffsetBaseForTesting(scroll_layer->id()));
         EXPECT_VECTOR_EQ(
-            gfx::Vector2dF(fmod(2.0f * scroll_amount_.x(), 1.0f), 0.0f),
+            scroll_amount_ + scroll_amount_ -
+                gfx::ToRoundedVector2d(scroll_amount_ + scroll_amount_),
             ScrollDelta(scroll_layer));
         EndTest();
         break;
     }
     scroll_layer->ScrollBy(scroll_amount_);
   }
 
   void AfterTest() override {}
 
  private:
@@ skipping 1741 matching lines @@
 
   const float initial_page_scale_ = 0.5f;
   const float page_scale_update_ = 0.2f;
 };
 
 // The reflected deltas are supported in threaded mode only.
 MULTI_THREAD_TEST_F(LayerTreeHostScrollTestAppliesReflectedDeltas);
 
 }  // namespace
 }  // namespace cc