ui: Prefer +/- operators to apply offsets.

ui/gfx/point_base.h

Index: ui/gfx/point_base.h
diff --git a/ui/gfx/point_base.h b/ui/gfx/point_base.h
index ae3342c4dcf1706fc2a9b6b71aab202437d89167..25785207011ea4316f7d43769a9fbbff5594396f 100644
--- a/ui/gfx/point_base.h
+++ b/ui/gfx/point_base.h
@@ -34,11 +34,13 @@ class UI_EXPORT PointBase {
   }
 
   void operator+=(const VectorClass& vector) {
-    Offset(vector.x(), vector.y());
+    x_ += vector.x();
+    y_ += vector.y();
   }
 
   void operator-=(const VectorClass& vector) {
-    Offset(-vector.x(), -vector.y());
+    x_ -= vector.x();
+    y_ -= vector.y();
   }
 
   bool IsOrigin() const {
@@ -49,10 +51,6 @@ class UI_EXPORT PointBase {
     return VectorClass(x_, y_);
   }
 
-  VectorClass OffsetFrom(const Class& other) const {
-    return VectorClass(x_ - other.x_, y_ - other.y_);
-  }
-
   // A point is less than another point if its y-value is closer
   // to the origin. If the y-values are the same, then point with
   // the x-value closer to the origin is considered less than the