Make RenderTextWin fallback match original font heights.

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 e76e6db39e8a55af31a8b1a0a1e0ad349bd86953..f7d5ce96ec66f985b8b97ebd973fd878024ead65 100644
--- a/ui/gfx/render_text_win.cc
+++ b/ui/gfx/render_text_win.cc
@@ -38,29 +38,13 @@ const size_t kMaxRuns = 10000;
 // The maximum number of glyphs per run; ScriptShape fails on larger values.
 const size_t kMaxGlyphs = 65535;
 
-// Changes |font| to have the specified |font_size| (or |font_height| on Windows
-// XP) and |font_style| if it is not the case already. Only considers bold and
-// italic styles, since the underlined style has no effect on glyph shaping.
-void DeriveFontIfNecessary(int font_size,
-                           int font_height,
-                           int font_style,
-                           Font* font) {
+// Changes |font| to the specified |font_height| and bold/italic |font_style|.
+// Underlined styling is not considered, as it has no effect on glyph shaping.
+void DeriveFontIfNecessary(int height, int style, Font* font) {
   const int kStyleMask = (Font::BOLD | Font::ITALIC);
-  const int target_style = (font_style & kStyleMask);
-
-  // On Windows XP, the font must be resized using |font_height| instead of
-  // |font_size| to match GDI behavior.
-  if (base::win::GetVersion() < base::win::VERSION_VISTA) {
-    PlatformFontWin* platform_font =
-        static_cast<PlatformFontWin*>(font->platform_font());
-    *font = platform_font->DeriveFontWithHeight(font_height, target_style);
-    return;
-  }
-
-  const int current_style = (font->GetStyle() & kStyleMask);
-  const int current_size = font->GetFontSize();
-  if (current_style != target_style || current_size != font_size)
-    *font = font->Derive(font_size - current_size, target_style);
+  PlatformFontWin* platform_font =
+      static_cast<PlatformFontWin*>(font->platform_font());
+  *font = platform_font->DeriveFontWithHeight(height, style & kStyleMask);
 }
 
 // Returns true if |c| is a Unicode BiDi control character.
@@ -891,8 +875,7 @@ void RenderTextWin::ItemizeLogicalText() {
     run->font = font_list().GetPrimaryFont();
     run->font_style = (style.style(BOLD) ? Font::BOLD : 0) |
                       (style.style(ITALIC) ? Font::ITALIC : 0);
-    DeriveFontIfNecessary(run->font.GetFontSize(), run->font.GetHeight(),
-                          run->font_style, &run->font);
+    DeriveFontIfNecessary(run->font.GetHeight(), run->font_style, &run->font);
     run->strike = style.style(STRIKE);
     run->diagonal_strike = style.style(DIAGONAL_STRIKE);
     run->underline = style.style(UNDERLINE);
@@ -1119,10 +1102,9 @@ HRESULT RenderTextWin::ShapeTextRunWithFont(internal::TextRun* run,
   // Update the run's font only if necessary. If the two fonts wrap the same
   // PlatformFontWin object, their native fonts will have the same value.
   if (run->font.GetNativeFont() != font.GetNativeFont()) {
-    const int font_size = run->font.GetFontSize();
-    const int font_height = run->font.GetHeight();
+    const int original_height = run->font.GetHeight();
     run->font = font;
-    DeriveFontIfNecessary(font_size, font_height, run->font_style, &run->font);
+    DeriveFontIfNecessary(original_height, run->font_style, &run->font);
     ScriptFreeCache(&run->script_cache);
   }