[RenderText] Added append text

ui/gfx/render_text.cc

Index: ui/gfx/render_text.cc
diff --git a/ui/gfx/render_text.cc b/ui/gfx/render_text.cc
index 2b51d8aa8c75156871e18fda188ba726cad0c33a..8d4140b6ac900df1e111bc7b8c254a3cfb2b2f19 100644
--- a/ui/gfx/render_text.cc
+++ b/ui/gfx/render_text.cc
@@ -446,19 +446,14 @@ void RenderText::SetText(const base::string16& text) {
   if (text_ == text)
     return;
   text_ = text;
+  UpdateStyleLengths();
 
-  // Adjust ranged styles, baselines, and colors to accommodate a new text
-  // length. Clear style ranges as they might break new text graphemes and apply
+  // Clear style ranges as they might break new text graphemes and apply
   // the first style to the whole text instead.
-  const size_t text_length = text_.length();
-  colors_.SetMax(text_length);
+  colors_.SetValue(colors_.breaks().begin()->second);
   baselines_.SetValue(baselines_.breaks().begin()->second);
-  baselines_.SetMax(text_length);
-  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style) {
-    BreakList<bool>& break_list = styles_[style];
-    break_list.SetValue(break_list.breaks().begin()->second);
-    break_list.SetMax(text_length);
-  }
+  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style)
+    styles_[style].SetValue(styles_[style].breaks().begin()->second);
   cached_bounds_and_offset_valid_ = false;
 
   // Reset selection model. SetText should always followed by SetSelectionModel
@@ -473,6 +468,14 @@ void RenderText::SetText(const base::string16& text) {
   OnTextAttributeChanged();
 }
 
+void RenderText::AppendText(const base::string16& text) {
+  text_ += text;
+  UpdateStyleLengths();
+  cached_bounds_and_offset_valid_ = false;
+  obscured_reveal_index_ = -1;
+  OnTextAttributeChanged();
+}
+
 void RenderText::SetHorizontalAlignment(HorizontalAlignment alignment) {
   if (horizontal_alignment_ != alignment) {
     horizontal_alignment_ = alignment;
@@ -1241,6 +1244,15 @@ size_t RenderText::TextIndexToGivenTextIndex(const base::string16& given_text,
   return std::min<size_t>(given_text.length(), i);
 }
 
+void RenderText::UpdateStyleLengths() {
+  // Adjust ranged styles and colors to accommodate a new text length.

[msw, 2015/03/20 00:24:11]

nit: remove this in favor of a comment in the header.

[dschuyler, 2015/03/20 00:46:16]

Done.

+  const size_t text_length = text_.length();
+  colors_.SetMax(text_length);
+  baselines_.SetMax(text_length);
+  for (size_t style = 0; style < NUM_TEXT_STYLES; ++style)
+    styles_[style].SetMax(text_length);
+}
+
 // static
 bool RenderText::RangeContainsCaret(const Range& range,
                                     size_t caret_pos,