ui: Prefer +/- operators to apply offsets.

ui/gfx/vector2d_f.h

 // Copyright (c) 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.
 
 // Defines a simple float vector class.  This class is used to indicate a
 // distance in two dimensions between two points. Subtracting two points should
 // produce a vector, and adding a vector to a point produces the point at the
 // vector's distance from the original point.
 
 #ifndef UI_GFX_VECTOR2D_F_H_
@@ skipping 64 matching lines @@
   result.Add(-rhs);
   return result;
 }
 
 // Return the cross product of two vectors.
 UI_EXPORT double CrossProduct(const Vector2dF& lhs, const Vector2dF& rhs);
 
 // Return the dot product of two vectors.
 UI_EXPORT double DotProduct(const Vector2dF& lhs, const Vector2dF& rhs);
 
+// Return a vector that is |v| scaled by the given scale factors along each
+// axis.
+UI_EXPORT Vector2dF ScaleVector2d(const Vector2dF& v,
+                                  float x_scale,
+                                  float y_scale);
+
+// Return a vector that is |v| scaled by the given scale factor.
+inline Vector2dF ScaleVector2d(const Vector2dF& v, float scale) {
+  return ScaleVector2d(v, scale, scale);
+}
+
 }  // namespace gfx
 
 #endif // UI_GFX_VECTOR2D_F_H_