Improve scroll performance on Windows 10 with high precision touchpads.

content/browser/renderer_host/legacy_render_widget_host_win.cc

Index: content/browser/renderer_host/legacy_render_widget_host_win.cc
diff --git a/content/browser/renderer_host/legacy_render_widget_host_win.cc b/content/browser/renderer_host/legacy_render_widget_host_win.cc
index 5126ad2bc2da97d1c829ad9f6913ecaeb5de0424..af9d6b229e1802bf5b3f3378a92ab283a5c8bff5 100644
--- a/content/browser/renderer_host/legacy_render_widget_host_win.cc
+++ b/content/browser/renderer_host/legacy_render_widget_host_win.cc
@@ -75,6 +75,8 @@ HWND LegacyRenderWidgetHostHWND::GetParent() {
 
 void LegacyRenderWidgetHostHWND::Show() {
   ::ShowWindow(hwnd(), SW_SHOW);
+  if (direct_manipulation_helper_)
+    direct_manipulation_helper_->Activate(hwnd());
 }
 
 void LegacyRenderWidgetHostHWND::Hide() {
@@ -86,6 +88,8 @@ void LegacyRenderWidgetHostHWND::SetBounds(const gfx::Rect& bounds) {
   ::SetWindowPos(hwnd(), NULL, bounds_in_pixel.x(), bounds_in_pixel.y(),
                  bounds_in_pixel.width(), bounds_in_pixel.height(),
                  SWP_NOREDRAW);
+  if (direct_manipulation_helper_)
+    direct_manipulation_helper_->SetBounds(bounds_in_pixel);
 }
 
 void LegacyRenderWidgetHostHWND::OnFinalMessage(HWND hwnd) {
@@ -126,6 +130,13 @@ bool LegacyRenderWidgetHostHWND::Init() {
                    CHILDID_SELF);
   }
 
+  // Direct Manipulation is enabled on Windows 10+. The CreateInstance function
+  // returns NULL if Direct Manipulation is not available.
+  direct_manipulation_helper_.reset(
+      gfx::win::DirectManipulationHelper::CreateInstance());
+  if (direct_manipulation_helper_)
+    direct_manipulation_helper_->Initialize(hwnd());
+
   return !!SUCCEEDED(hr);
 }
 
@@ -242,6 +253,12 @@ LRESULT LegacyRenderWidgetHostHWND::OnMouseRange(UINT message,
       handled = TRUE;
     }
   }
+
+  if (direct_manipulation_helper_ &&
+      (message == WM_MOUSEWHEEL || message == WM_MOUSEHWHEEL)) {
+    direct_manipulation_helper_->HandleMouseWheel(hwnd(), message, w_param,
+        l_param);
+  }
   return ret;
 }