Add Vector2d classes that represent offsets, instead of using Point.

ui/gfx/vector2d_f.cc

Index: ui/gfx/vector2d_f.cc
diff --git a/ui/gfx/insets_f.cc b/ui/gfx/vector2d_f.cc
similarity index 50%
copy from ui/gfx/insets_f.cc
copy to ui/gfx/vector2d_f.cc
index 54aa131bbf9330b6e393ee0e5b4d70c70392bbf0..b95a2bc35f8d850fbe531d143b57cf159f360ccc 100644
--- a/ui/gfx/insets_f.cc
+++ b/ui/gfx/vector2d_f.cc
@@ -2,15 +2,23 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ui/gfx/insets_f.h"
-
 #include "base/stringprintf.h"
+#include "ui/gfx/vector2d_f.h"
 
 namespace gfx {
 
-std::string InsetsF::ToString() const {
-  // Print members in the same order of the constructor parameters.
-  return StringPrintf("%f,%f,%f,%f", top_,  left_, bottom_, right_);
+Vector2dF::Vector2dF()
+    : x_(0),
+      y_(0) {
+}
+
+Vector2dF::Vector2dF(float x, float y)
+    : x_(x),
+      y_(y) {
+}
+
+std::string Vector2dF::ToString() const {
+  return base::StringPrintf("[%f %f]", x_, y_);
 }
 
 }  // namespace gfx