Use float for scroll offset.

ui/gfx/geometry/scroll_offset.h

 // Copyright 2014 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.
 
 #ifndef UI_GFX_GEOMETRY_SCROLL_OFFSET_H_
 #define UI_GFX_GEOMETRY_SCROLL_OFFSET_H_
 
 #include <iosfwd>
 #include <string>
 
 #include "ui/gfx/geometry/safe_integer_conversions.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/gfx_export.h"
 
 namespace gfx {
 
+// TODO(szager): Reconcile terminology with blink.  An 'offset' here corresponds
+// to a 'position' in blink.  In blink, 'offset' means something else.  See
+// third_party/WebKit/Source/core/layout/README.md for more information.
+
 class GFX_EXPORT ScrollOffset {
  public:
   ScrollOffset() : x_(0), y_(0) {}
-  ScrollOffset(double x, double y) : x_(x), y_(y) {}
+  ScrollOffset(float x, float y) : x_(x), y_(y) {}
   explicit ScrollOffset(const Vector2dF& v) : x_(v.x()), y_(v.y()) {}
   explicit ScrollOffset(const Vector2d& v) : x_(v.x()), y_(v.y()) {}
 
-  double x() const { return x_; }
-  void set_x(double x) { x_ = x; }
+  float x() const { return x_; }
+  void set_x(float x) { x_ = x; }
 
-  double y() const { return y_; }
-  void set_y(double y) { y_ = y; }
+  float y() const { return y_; }
+  void set_y(float y) { y_ = y; }
 
   // True if both components are 0.
   bool IsZero() const {
     return x_ == 0 && y_ == 0;
   }
 
   // Add the components of the |other| ScrollOffset to the current ScrollOffset.
   void Add(const ScrollOffset& other) {
     x_ += other.x_;
     y_ += other.y_;
@@ skipping 16 matching lines @@
   void SetToMin(const ScrollOffset& other) {
     x_ = x_ <= other.x_ ? x_ : other.x_;
     y_ = y_ <= other.y_ ? y_ : other.y_;
   }
 
   void SetToMax(const ScrollOffset& other) {
     x_ = x_ >= other.x_ ? x_ : other.x_;
     y_ = y_ >= other.y_ ? y_ : other.y_;
   }
 
-  void Scale(double scale) { Scale(scale, scale); }
-  void Scale(double x_scale, double y_scale) {
+  void Scale(float scale) { Scale(scale, scale); }
+  void Scale(float x_scale, float y_scale) {
     x_ *= x_scale;
     y_ *= y_scale;
   }
 
   std::string ToString() const;
 
  private:
-  double x_;
-  double y_;
+  float x_;
+  float y_;
 };
 
 inline bool operator==(const ScrollOffset& lhs, const ScrollOffset& rhs) {
   return lhs.x() == rhs.x() && lhs.y() == rhs.y();
 }
 
 inline bool operator!=(const ScrollOffset& lhs, const ScrollOffset& rhs) {
   return lhs.x() != rhs.x() || lhs.y() != rhs.y();
 }
 
@@ skipping 30 matching lines @@
 }
 
 // This is declared here for use in gtest-based unit tests but is defined in
 // the //ui/gfx:test_support target. Depend on that to use this in your unit
 // test. This should not be used in production code - call ToString() instead.
 void PrintTo(const ScrollOffset& scroll_offset, ::std::ostream* os);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GEOMETRY_SCROLL_OFFSET_H_