Add an option to create unpremultiplied bitmaps.

src/core/SkDevice.cpp

Index: src/core/SkDevice.cpp
diff --git a/src/core/SkDevice.cpp b/src/core/SkDevice.cpp
index dee5bc76afb67a85d796d73905ddd365e3fdce8d..ffb2fcc1e15b1cd56acbc5f793fdebecd4cc0d83 100644
--- a/src/core/SkDevice.cpp
+++ b/src/core/SkDevice.cpp
@@ -30,6 +30,8 @@ SkDevice::SkDevice(const SkBitmap& bitmap)
     , fAttachedToCanvas(false)
 #endif
 {
+    SkASSERT(bitmap.config() != SkBitmap::kIndex8_Config);
+    SkASSERT(bitmap.premultiplied());
     fOrigin.setZero();
     fMetaData = NULL;
 }
@@ -40,6 +42,8 @@ SkDevice::SkDevice(const SkBitmap& bitmap, const SkDeviceProperties& devicePrope
     , fAttachedToCanvas(false)
 #endif
 {
+    SkASSERT(bitmap.config() != SkBitmap::kIndex8_Config);
+    SkASSERT(bitmap.premultiplied());
     fOrigin.setZero();
     fMetaData = NULL;
 }
@@ -53,6 +57,9 @@ SkDevice::SkDevice(SkBitmap::Config config, int width, int height, bool isOpaque
     fOrigin.setZero();
     fMetaData = NULL;
 
+    if (SkBitmap::kIndex8_Config == config) {
+        config = SkBitmap::kARGB_8888_Config;
+    }
     fBitmap.setConfig(config, width, height);
     fBitmap.allocPixels();
     fBitmap.setIsOpaque(isOpaque);
@@ -71,6 +78,9 @@ SkDevice::SkDevice(SkBitmap::Config config, int width, int height, bool isOpaque
     fOrigin.setZero();
     fMetaData = NULL;
 
+    if (SkBitmap::kIndex8_Config == config) {
+        config = SkBitmap::kARGB_8888_Config;
+    }
     fBitmap.setConfig(config, width, height);
     fBitmap.allocPixels();
     fBitmap.setIsOpaque(isOpaque);
@@ -84,6 +94,8 @@ SkDevice::~SkDevice() {
 }
 
 void SkDevice::replaceBitmapBackendForRasterSurface(const SkBitmap& bm) {
+    SkASSERT(bm.config() != SkBitmap::kIndex8_Config);
+    SkASSERT(bm.premultiplied());
     SkASSERT(bm.width() == fBitmap.width());
     SkASSERT(bm.height() == fBitmap.height());
     fBitmap = bm;   // intent is to use bm's pixelRef (and rowbytes/config)
@@ -108,6 +120,9 @@ SkDevice* SkDevice::onCreateCompatibleDevice(SkBitmap::Config config,
                                              int width, int height,
                                              bool isOpaque,
                                              Usage usage) {
+    if (SkBitmap::kIndex8_Config == config) {
+        config = SkBitmap::kARGB_8888_Config;
+    }
     return SkNEW_ARGS(SkDevice,(config, width, height, isOpaque, fLeakyProperties));
 }