Media Controls: move timeline related code to modules.

third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h

Index: third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h
diff --git a/third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h b/third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h
index 0a5137397e1a2a008e2c1cb1a4a62ef4ef07e0d1..1583de3ee16dcb1fb34ebe9c21ed2c2871ca0149 100644
--- a/third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h
+++ b/third_party/WebKit/Source/core/layout/api/LayoutSliderItem.h
@@ -1,4 +1,3 @@
-
 // Copyright 2016 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.
@@ -6,6 +5,7 @@
 #ifndef LayoutSliderItem_h
 #define LayoutSliderItem_h
 
+#include "core/CoreExport.h"
 #include "core/layout/LayoutSlider.h"
 #include "core/layout/api/LayoutBlockItem.h"
 
@@ -23,9 +23,9 @@ class LayoutSliderItem : public LayoutBlockItem {
 
   explicit LayoutSliderItem(std::nullptr_t) : LayoutBlockItem(nullptr) {}
 
-  LayoutSliderItem() {}
+  LayoutSliderItem() = default;
 
-  bool InDragMode() const { return ToSlider()->InDragMode(); }
+  CORE_EXPORT bool InDragMode() const { return ToSlider()->InDragMode(); }
 
  private:
   LayoutSlider* ToSlider() { return ToLayoutSlider(GetLayoutObject()); }