Switch gfx::Range to use uint32_t instead of size_t.

ui/gfx/selection_model.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.
 
 #ifndef UI_GFX_SELECTION_MODEL_H_
 #define UI_GFX_SELECTION_MODEL_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 59 matching lines @@
   // Create a SelectionModel representing a selection (which may be empty).
   // The caret position is the end of the range.
   SelectionModel(const Range& selection, LogicalCursorDirection affinity);
 
   const Range& selection() const { return selection_; }
   size_t caret_pos() const { return selection_.end(); }
   LogicalCursorDirection caret_affinity() const { return caret_affinity_; }
 
   // WARNING: Generally the selection start should not be changed without
   // considering the effect on the caret affinity.
-  void set_selection_start(size_t pos) { selection_.set_start(pos); }
+  void set_selection_start(uint32_t pos) { selection_.set_start(pos); }
 
   bool operator==(const SelectionModel& sel) const;
   bool operator!=(const SelectionModel& sel) const { return !(*this == sel); }
 
   std::string ToString() const;
 
  private:
   // Logical selection. The logical caret position is the end of the selection.
   Range selection_;
 
@@ skipping 12 matching lines @@
   //          3                  abc|FED                     abcFED|
   //          4                  abcFE|D                     abcFE|D
   //          5                  abcF|ED                     abcF|ED
   //          6                  abc|FED                     abcFED|
   LogicalCursorDirection caret_affinity_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SELECTION_MODEL_H_