Attempt at getting GDI text to render when drawn using canvas. I added...

third_party/WebKit/WebCore/platform/graphics/chromium/FontChromiumWin.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Computer, Inc.
  * Copyright (c) 2006, 2007, 2008, 2009, Google Inc. All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  * 
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 156 matching lines @@
 
 void Font::drawGlyphs(GraphicsContext* graphicsContext,
                       const SimpleFontData* font,
                       const GlyphBuffer& glyphBuffer,
                       int from,
                       int numGlyphs,
                       const FloatPoint& point) const
 {
     PlatformGraphicsContext* context = graphicsContext->platformContext();
 
+    bool canUseGDI = windowsCanHandleTextDrawing(graphicsContext);
+    bool createdLayer = false;
+
+    if (canUseGDI && context->isDrawingToImageBuffer()) {
+        // We're drawing to an image buffer and about to render text with GDI.
+        // We need to start a layer here, otherwise the alpha values rendered
+        // by GDI are never correctly updated.
+        // NOTE: this doesn't handle clear type well and should be removed when
+        // we have better text handling code.
+        graphicsContext->beginTransparencyLayer(1.0);
+        createdLayer = true;
+    }
+
     // Max buffer length passed to the underlying windows API.
     const int kMaxBufferLength = 1024;
     // Default size for the buffer. It should be enough for most of cases.
     const int kDefaultBufferLength = 256;
 
     SkColor color = context->fillColor();
     unsigned char alpha = SkColorGetA(color);
     // Skip 100% transparent text; no need to draw anything.
     if (!alpha && context->getStrokeStyle() == NoStroke)
         return;
@@ skipping 11 matching lines @@
     // Windows needs the characters and the advances in nice contiguous
     // buffers, which we build here.
     Vector<WORD, kDefaultBufferLength> glyphs;
     Vector<int, kDefaultBufferLength> advances;
 
     // Compute the coordinate. The 'origin' represents the baseline, so we need
     // to move it up to the top of the bounding square.
     int x = static_cast<int>(point.x());
     int lineTop = static_cast<int>(point.y()) - font->ascent();
 
-    bool canUseGDI = windowsCanHandleTextDrawing(graphicsContext);
-
     // We draw the glyphs in chunks to avoid having to do a heap allocation for
     // the arrays of characters and advances. Since ExtTextOut is the
     // lowest-level text output function on Windows, there should be little
     // penalty for splitting up the text. On the other hand, the buffer cannot
     // be bigger than 4094 or the function will fail.
     int glyphIndex = 0;
     while (glyphIndex < numGlyphs) {
         // how many chars will be in this chunk?
         int curLen = std::min(kMaxBufferLength, numGlyphs - glyphIndex);
 
@@ skipping 25 matching lines @@
             }
             break;
         }
 
         ASSERT(success);
 
         x += curWidth;
     }
 
     SelectObject(hdc, oldFont);
+    if (createdLayer)
+        graphicsContext->endTransparencyLayer();
     context->canvas()->endPlatformPaint();
 }
 
 FloatRect Font::selectionRectForComplexText(const TextRun& run,
                                             const IntPoint& point,
                                             int h,
                                             int from,
                                             int to) const
 {
     UniscribeHelperTextRun state(run, *this);
@@ skipping 53 matching lines @@
     int charIndex = state.xToCharacter(x);
 
     // XToCharacter will return -1 if the position is before the first
     // character (we get called like this sometimes).
     if (charIndex < 0)
         charIndex = 0;
     return charIndex;
 }
 
 } // namespace WebCore