Implement windows mousewheel scroll by page functionality

cc/trees/layer_tree_host_impl_unittest.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 "cc/trees/layer_tree_host_impl.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 524 matching lines @@
 
     // Scrolling diagonally against an edge will succeed.
     EXPECT_TRUE(m_hostImpl->ScrollBy(gfx::Point(), gfx::Vector2d(10, -10)));
     EXPECT_TRUE(m_hostImpl->ScrollBy(gfx::Point(), gfx::Vector2d(-10, 0)));
     EXPECT_TRUE(m_hostImpl->ScrollBy(gfx::Point(), gfx::Vector2d(-10, 10)));
 
     // Trying to scroll more than the available space will also succeed.
     EXPECT_TRUE(m_hostImpl->ScrollBy(gfx::Point(), gfx::Vector2d(5000, 5000)));
 }
 
+TEST_F(LayerTreeHostImplTest, scrollVerticallyByPageReturnsCorrectValue)
+{
+    setupScrollAndContentsLayers(gfx::Size(200, 2000));
+    m_hostImpl->SetViewportSize(gfx::Size(100, 1000), gfx::Size(100, 1000));
+
+    initializeRendererAndDrawFrame();
+
+    EXPECT_EQ(InputHandlerClient::ScrollStarted,
+        m_hostImpl->ScrollBegin(gfx::Point(0, 0), InputHandlerClient::Wheel));
+
+    // Trying to scroll without a vertical scrollbar will fail.
+    EXPECT_FALSE(m_hostImpl->ScrollVerticallyByPage(
+          gfx::Point(), WebKit::WebScrollbar::ScrollForward));
+    EXPECT_FALSE(m_hostImpl->ScrollVerticallyByPage(
+          gfx::Point(), WebKit::WebScrollbar::ScrollBackward));
+
+    scoped_ptr<cc::ScrollbarLayerImpl> vertical_scrollbar(
+        cc::ScrollbarLayerImpl::Create(
+            m_hostImpl->active_tree(),
+            20,
+            scoped_ptr<ScrollbarGeometryFixedThumb>()));
+    vertical_scrollbar->SetBounds(gfx::Size(15, 1000));
+    m_hostImpl->RootScrollLayer()->SetVerticalScrollbarLayer(
+        vertical_scrollbar.get());
+
+    // Trying to scroll with a vertical scrollbar will succeed.
+    EXPECT_TRUE(m_hostImpl->ScrollVerticallyByPage(
+          gfx::Point(), WebKit::WebScrollbar::ScrollForward));
+    EXPECT_FLOAT_EQ(875.f, m_hostImpl->RootScrollLayer()->scroll_delta().y());
+    EXPECT_TRUE(m_hostImpl->ScrollVerticallyByPage(
+          gfx::Point(), WebKit::WebScrollbar::ScrollBackward));
+}
+
 TEST_F(LayerTreeHostImplTest, clearRootRenderSurfaceAndHitTestTouchHandlerRegion)
 {
     setupScrollAndContentsLayers(gfx::Size(100, 100));
     m_hostImpl->SetViewportSize(gfx::Size(50, 50), gfx::Size(50, 50));
     initializeRendererAndDrawFrame();
 
     // We should be able to hit test for touch event handlers even if the root layer loses
     // its render surface after the most recent render.
     m_hostImpl->active_tree()->root_layer()->ClearRenderSurface();
     m_hostImpl->active_tree()->set_needs_update_draw_properties();
@@ skipping 3789 matching lines @@
         EXPECT_EQ(gfx::Rect(0, 0, 100, 100).ToString(), renderPassQuad->rect.ToString());
         EXPECT_EQ(gfx::RectF(0.f, 0.f, 1.f, 1.f).ToString(), renderPassQuad->mask_uv_rect.ToString());
 
         m_hostImpl->DrawLayers(&frame, base::TimeTicks::Now());
         m_hostImpl->DidDrawAllLayers(frame);
     }
 }
 
 }  // namespace
 }  // namespace cc