[WIP: not for review] Reduce re-layout

ui/gfx/render_text.h

Index: ui/gfx/render_text.h
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
index 32ad44bf5ed3433f56f8a02282c9b1eec57155db..f27293b646177ef070dbe0b247bcf60dd56ac2e4 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -211,6 +211,10 @@ class GFX_EXPORT RenderText {
   // Creates another instance of the same concrete class.
   virtual std::unique_ptr<RenderText> CreateInstanceOfSameType() const = 0;
 
+  // Like above but copies all style settings too.
+  std::unique_ptr<RenderText> CreateInstanceOfSameStyle(
+      const base::string16& text) const;
+
   const base::string16& text() const { return text_; }
   void SetText(const base::string16& text);
   void AppendText(const base::string16& text);
@@ -266,6 +270,12 @@ class GFX_EXPORT RenderText {
   bool multiline() const { return multiline_; }
   void SetMultiline(bool multiline);
 
+  // If multiline, a non-zero value will cap the number of lines rendered,
+  // and elide the rest (currently only ELIDE_TAIL supported.)
+  void SetMaxLines(size_t max_lines);
+  size_t max_lines() const { return max_lines_; }
+  size_t GetNumLines();
+
   // TODO(mukai): ELIDE_LONG_WORDS is not supported.
   WordWrapBehavior word_wrap_behavior() const { return word_wrap_behavior_; }
   void SetWordWrapBehavior(WordWrapBehavior behavior);
@@ -778,6 +788,9 @@ class GFX_EXPORT RenderText {
   // |display_rect_| as the width cap.
   bool multiline_;
 
+  // If multiple lines, the maximum number of lines to render, or 0.
+  size_t max_lines_;
+
   // The wrap behavior when the text is broken into lines. Do nothing unless
   // |multiline_| is set. The default value is IGNORE_LONG_WORDS.
   WordWrapBehavior word_wrap_behavior_;