Cache a screen compatible DC to avoid re-creating it excessively.

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
===================================================================
--- ui/gfx/render_text_win.cc	(revision 120360)
+++ ui/gfx/render_text_win.cc	(working copy)
@@ -11,7 +11,7 @@
 #include "base/stl_util.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
-#include "base/win/scoped_hdc.h"
+#include "ui/gfx/screen_compatible_dc_win.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia.h"
 #include "ui/gfx/platform_font.h"
@@ -595,7 +595,7 @@
 
 void RenderTextWin::LayoutVisualText() {
   HRESULT hr = E_FAIL;
-  base::win::ScopedCreateDC hdc(CreateCompatibleDC(NULL));
+  ScopedTemporaryScreenCompatibleDC hdc;
   std::vector<internal::TextRun*>::const_iterator run_iter;
   for (run_iter = runs_.begin(); run_iter < runs_.end(); ++run_iter) {
     internal::TextRun* run = *run_iter;
@@ -604,7 +604,7 @@
     bool tried_fallback = false;
 
     // Select the font desired for glyph generation.
-    SelectObject(hdc, run->font.GetNativeFont());
+    SelectObject(hdc.get(), run->font.GetNativeFont());
 
     run->logical_clusters.reset(new WORD[run_length]);
     run->glyph_count = 0;
@@ -613,7 +613,7 @@
     while (max_glyphs < kMaxGlyphs) {
       run->glyphs.reset(new WORD[max_glyphs]);
       run->visible_attributes.reset(new SCRIPT_VISATTR[max_glyphs]);
-      hr = ScriptShape(hdc,
+      hr = ScriptShape(hdc.get(),
                        &run->script_cache,
                        run_text,
                        run_length,
@@ -644,10 +644,10 @@
 
         // The run's font doesn't contain the required glyphs, use an alternate.
         // TODO(msw): support RenderText's font_list().
-        if (ChooseFallbackFont(hdc, run->font, run_text, run_length,
+        if (ChooseFallbackFont(hdc.get(), run->font, run_text, run_length,
                                &run->font)) {
           ScriptFreeCache(&run->script_cache);
-          SelectObject(hdc, run->font.GetNativeFont());
+          SelectObject(hdc.get(), run->font.GetNativeFont());
         }
 
         tried_fallback = true;
@@ -660,7 +660,7 @@
     if (run->glyph_count > 0) {
       run->advance_widths.reset(new int[run->glyph_count]);
       run->offsets.reset(new GOFFSET[run->glyph_count]);
-      hr = ScriptPlace(hdc,
+      hr = ScriptPlace(hdc.get(),
                        &run->script_cache,
                        run->glyphs.get(),
                        run->glyph_count,