Don't paint text outside display area

ui/gfx/render_text_pango.cc

Index: ui/gfx/render_text_pango.cc
diff --git a/ui/gfx/render_text_pango.cc b/ui/gfx/render_text_pango.cc
index 07cbfb93cdf5c0e71d09261b618bd009028ba17c..27f00461093003ac75910ee677ca6271d60b70a1 100644
--- a/ui/gfx/render_text_pango.cc
+++ b/ui/gfx/render_text_pango.cc
@@ -410,9 +410,12 @@ void RenderTextPango::DrawVisualText(Canvas* canvas) {
 
   internal::StyleIterator style(colors(), styles());
   for (GSList* it = current_line_->runs; it; it = it->next) {
+    // Skip painting runs outside the display area.
+    if (SkScalarTruncToInt(x) >= display_rect().right())
+      break;
+
     PangoLayoutRun* run = reinterpret_cast<PangoLayoutRun*>(it->data);
     int glyph_count = run->glyphs->num_glyphs;
-    // TODO(msw): Skip painting runs outside the display rect area, like Win.
     if (glyph_count == 0)
       continue;
 
@@ -446,9 +449,13 @@ void RenderTextPango::DrawVisualText(Canvas* canvas) {
       x += pango_units_to_double(glyph.geometry.width);
 
       ++glyph_index;
+      // If this is the last glyph of the range or the last glyph inside the
+      // display area (which would cause early termination of the loop), paint
+      // the range.
       const size_t glyph_text_index = (glyph_index == glyph_count) ?
           style_range.end() : GetGlyphTextIndex(run, glyph_index);
-      if (!IndexInRange(style_range, glyph_text_index)) {
+      if (!IndexInRange(style_range, glyph_text_index) ||
+          SkScalarTruncToInt(x) >= display_rect().right()) {
         // TODO(asvitkine): For cases like "fi", where "fi" is a single glyph
         //                  but can span multiple styles, Pango splits the
         //                  styles evenly over the glyph. We can do this too by
@@ -470,7 +477,10 @@ void RenderTextPango::DrawVisualText(Canvas* canvas) {
         style_start_glyph_index = glyph_index;
         style_start_x = x;
       }
-    } while (glyph_index < glyph_count);
+      // Terminates loop when the end of the range has been reached or the next
+      // glyph falls outside the display area.
+    } while (glyph_index < glyph_count &&
+             SkScalarTruncToInt(x) < display_rect().right());
   }
 
   renderer.EndDiagonalStrike();