ui: Prefer +/- operators to apply offsets.

ui/gfx/vector2d_f.h

Index: ui/gfx/vector2d_f.h
diff --git a/ui/gfx/vector2d_f.h b/ui/gfx/vector2d_f.h
index e78c68821b7f2f18d85decfccc30a7ba61a9bddd..a245bb33882d4a670e964bcbfc660bed1a1082ef 100644
--- a/ui/gfx/vector2d_f.h
+++ b/ui/gfx/vector2d_f.h
@@ -82,6 +82,17 @@ 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_