Cache gfx::RenderText instances in views::Label.

ui/gfx/render_text.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_RENDER_TEXT_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <algorithm>
 #include <cstring>
 #include <string>
@@ skipping 238 matching lines @@
   // is cleared and only the last set index will be revealed. If |index| is -1
   // or out of range, no char will be revealed. The revealed index is also
   // cleared when SetText or SetObscured is called.
   void SetObscuredRevealIndex(int index);
 
   // TODO(ckocagil): Multiline text rendering is currently only supported on
   // Windows. Support other platforms.
   bool multiline() const { return multiline_; }
   void SetMultiline(bool multiline);
 
+  // Returns true if this supports multiline rendering.

[msw, 2015/02/20 01:55:53]

nit: "this instance"

[Jun Mukai, 2015/02/25 21:15:40]

Done.

+  virtual bool MultilineSupported() const = 0;
+
   // TODO(ckocagil): Add vertical alignment and line spacing support instead.
   int min_line_height() const { return min_line_height_; }
   void SetMinLineHeight(int line_height);
 
   // Set the maximum length of the layout text, not the actual text.
   // A |length| of 0 forgoes a hard limit, but does not guarantee proper
   // functionality of very long strings. Applies to subsequent SetText calls.
   // WARNING: Only use this for system limits, it lacks complex text support.
   void set_truncate_length(size_t length) { truncate_length_ = length; }
 
@@ skipping 152 matching lines @@
   // supplied index is already at the boundary of the string.
   size_t IndexOfAdjacentGrapheme(size_t index,
                                  LogicalCursorDirection direction);
 
   // Return a SelectionModel with the cursor at the current selection's start.
   // The returned value represents a cursor/caret position without a selection.
   SelectionModel GetSelectionModelForSelectionStart();
 
   // Sets shadows to drawn with text.
   void set_shadows(const ShadowValues& shadows) { shadows_ = shadows; }
-  const ShadowValues& shadows() { return shadows_; }
+  const ShadowValues& shadows() const { return shadows_; }
 
   typedef std::pair<Font, Range> FontSpan;
   // For testing purposes, returns which fonts were chosen for which parts of
   // the text by returning a vector of Font and Range pairs, where each range
   // specifies the character range for which the corresponding font has been
   // chosen.
   virtual std::vector<FontSpan> GetFontSpansForTesting() = 0;
 
   // Gets the horizontal bounds (relative to the left of the text, not the view)
   // of the glyph starting at |index|. If the glyph is RTL then the returned
@@ skipping 327 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated upon
   // OnLayoutTextAttributeChanged and OnDisplayTextAttributeChanged calls.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_