Revert of Fix Views inline autocomplete with multi-char graphemes.

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
diff --git a/ui/gfx/render_text_win.cc b/ui/gfx/render_text_win.cc
index 54e3931abb0c36e56ec3c906be4bcc743a957216..46f46dd85c19b79609bc6299fb36d11b9f2d096f 100644
--- a/ui/gfx/render_text_win.cc
+++ b/ui/gfx/render_text_win.cc
@@ -504,14 +504,19 @@
 // static
 std::map<std::string, Font> RenderTextWin::successful_substitute_fonts_;
 
-RenderTextWin::RenderTextWin() : RenderText(), needs_layout_(false) {
+RenderTextWin::RenderTextWin()
+    : RenderText(),
+      needs_layout_(false) {
   set_truncate_length(kMaxUniscribeTextLength);
+
   memset(&script_control_, 0, sizeof(script_control_));
   memset(&script_state_, 0, sizeof(script_state_));
+
   MoveCursorTo(EdgeSelectionModel(CURSOR_LEFT));
 }
 
-RenderTextWin::~RenderTextWin() {}
+RenderTextWin::~RenderTextWin() {
+}
 
 Size RenderTextWin::GetStringSize() {
   EnsureLayout();
@@ -711,7 +716,7 @@
 
 size_t RenderTextWin::TextIndexToLayoutIndex(size_t index) const {
   DCHECK_LE(index, text().length());
-  ptrdiff_t i = obscured() ? UTF16IndexToOffset(text(), 0, index) : index;
+  ptrdiff_t i = obscured() ? gfx::UTF16IndexToOffset(text(), 0, index) : index;
   CHECK_GE(i, 0);
   // Clamp layout indices to the length of the text actually used for layout.
   return std::min<size_t>(GetLayoutText().length(), i);
@@ -722,22 +727,24 @@
     return index;
 
   DCHECK_LE(index, GetLayoutText().length());
-  const size_t text_index = UTF16OffsetToIndex(text(), 0, index);
+  const size_t text_index = gfx::UTF16OffsetToIndex(text(), 0, index);
   DCHECK_LE(text_index, text().length());
   return text_index;
 }
 
-bool RenderTextWin::IsValidCursorIndex(size_t index) {
-  if (index == 0 || index == text().length())
+bool RenderTextWin::IsCursorablePosition(size_t position) {
+  if (position == 0 || position == text().length())
     return true;
-  if (!IsValidLogicalIndex(index))
-    return false;
   EnsureLayout();
-  // Disallow indices amid multi-character graphemes by checking glyph bounds.
-  // These characters are not surrogate-pairs, but may yield a single glyph:
-  //   \x0915\x093f - (ki) - one of many Devanagari biconsonantal conjuncts.
-  //   \x0e08\x0e33 - (cho chan + sara am) - a Thai consonant and vowel pair.
-  return GetGlyphBounds(index) != GetGlyphBounds(index - 1);
+
+  // Check that the index is at a valid code point (not mid-surrgate-pair),
+  // that it is not truncated from layout text (its glyph is shown on screen),
+  // and that its glyph has distinct bounds (not mid-multi-character-grapheme).
+  // An example of a multi-character-grapheme that is not a surrogate-pair is:
+  // \x0915\x093f - (ki) - one of many Devanagari biconsonantal conjuncts.
+  return gfx::IsValidCodePointIndex(text(), position) &&
+         position < LayoutIndexToTextIndex(GetLayoutText().length()) &&
+         GetGlyphBounds(position) != GetGlyphBounds(position - 1);
 }
 
 void RenderTextWin::ResetLayout() {
@@ -853,13 +860,8 @@
         const Range intersection =
             colors().GetRange(it).Intersect(segment->char_range);
         const Range colored_glyphs = CharRangeToGlyphRange(*run, intersection);
-        // The range may be empty if a portion of a multi-character grapheme is
-        // selected, yielding two colors for a single glyph. For now, this just
-        // paints the glyph with a single style, but it should paint it twice,
-        // clipped according to selection bounds. See http://crbug.com/366786
-        if (colored_glyphs.is_empty())
-          continue;
         DCHECK(glyph_range.Contains(colored_glyphs));
+        DCHECK(!colored_glyphs.is_empty());
         const SkPoint& start_pos =
             pos[colored_glyphs.start() - glyph_range.start()];
         const SkPoint& end_pos =