add new readPixels with direct memory parameters

tools/sk_tool_utils.cpp

Index: tools/sk_tool_utils.cpp
diff --git a/tools/sk_tool_utils.cpp b/tools/sk_tool_utils.cpp
index 11973886949baf9542c9baa900bc7ad68bd88858..d13b0d81f8e2561fdd01cf1b0cae5d38a04f7b2f 100644
--- a/tools/sk_tool_utils.cpp
+++ b/tools/sk_tool_utils.cpp
@@ -2,6 +2,21 @@
 
 namespace sk_tool_utils {
 
+const char* colortype_name(SkColorType ct) {
+    switch (ct) {
+        case kUnknown_SkColorType:      return "Unknown";
+        case kAlpha_8_SkColorType:      return "Alpha_8";
+        case kIndex_8_SkColorType:      return "Index_8";
+        case kARGB_4444_SkColorType:    return "ARGB_4444";
+        case kRGB_565_SkColorType:      return "RGB_565";
+        case kRGBA_8888_SkColorType:    return "RGBA_8888";
+        case kBGRA_8888_SkColorType:    return "BGRA_8888";
+        default:
+            SkASSERT(false);
+            return "unexpected colortype";
+    }
+}
+
 void config8888_to_imagetypes(SkCanvas::Config8888 config, SkColorType* ct, SkAlphaType* at) {
     switch (config) {
         case SkCanvas::kNative_Premul_Config8888: