Expand pixelref to return SkImageInfo and rowbytes

include/core/SkImageInfo.h

Index: include/core/SkImageInfo.h
diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index c22249b842aaf3f602c5e3b99e57ce1bdaff7b42..565105b07bee1bf83b1dd8ca3decb1eeb96884ce 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -63,6 +63,7 @@ static inline bool SkAlphaTypeIsOpaque(SkAlphaType at) {
 enum SkColorType {
     kAlpha_8_SkColorType,
     kRGB_565_SkColorType,
+    kARGB_4444_SkColorType,
     kRGBA_8888_SkColorType,
     kBGRA_8888_SkColorType,
     kIndex8_SkColorType,
@@ -82,6 +83,7 @@ static int SkColorTypeBytesPerPixel(SkColorType ct) {
     static const uint8_t gSize[] = {
         1,  // Alpha_8
         2,  // RGB_565
+        2,  // ARGB_4444
         4,  // RGBA_8888
         4,  // BGRA_8888
         1,  // kIndex_8
@@ -112,12 +114,27 @@ struct SkImageInfo {
         return SkColorTypeBytesPerPixel(fColorType);
     }
 
+    size_t minRowBytes() const {
+        return fWidth * this->bytesPerPixel();
+    }
+
     bool operator==(const SkImageInfo& other) const {
         return 0 == memcmp(this, &other, sizeof(other));
     }
     bool operator!=(const SkImageInfo& other) const {
         return 0 != memcmp(this, &other, sizeof(other));
     }
+
+    bool isValid() const {
+        return  fWidth >= 0 &&
+                fHeight >= 0 &&
+                fColorType <= kLastEnum_SkColorType &&
+                fAlphaType <= kLastEnum_SkAlphaType;
+    }
+
+    void validate() const {
+        SkASSERT(this->isValid());
+    }
 };
 
 #endif