Modify SkPngCodec to recognize 565 images from the sBIT chunk

include/codec/SkEncodedInfo.h

Index: include/codec/SkEncodedInfo.h
diff --git a/include/codec/SkEncodedInfo.h b/include/codec/SkEncodedInfo.h
index eb8c147a3b7037ab16a675197bdf9ec7a51ef096..3b6fcbf2dd18915c626054bebc0d94d814132b2e 100644
--- a/include/codec/SkEncodedInfo.h
+++ b/include/codec/SkEncodedInfo.h
@@ -65,6 +65,13 @@ public:
         // be treated as inverted CMYK.
         kInvertedCMYK_Color,
         kYCCK_Color,
+
+        // PNG
+        // 565 images may be encoded to PNG by specifying the number of
+        // significant bits for each channel.  This is a strange 565
+        // representation because the image is still encoded with 8 bits per
+        // component.
+        k565_Color,
     };
 
     static SkEncodedInfo Make(Color color, Alpha alpha, int bitsPerComponent) {
@@ -105,8 +112,8 @@ public:
                 SkASSERT(kOpaque_Alpha != alpha);
                 SkASSERT(8 == bitsPerComponent);
                 break;
-            default:

[mtklein, 2016/08/04 17:52:51]

No need for defaults anymore?

[msarett, 2016/08/04 19:04:10]

Yeah, all values of the enum are handled.  This used to not be true, before I
deleted kUnknown.

-                SkASSERT(false);
+            case k565_Color:
+                SkASSERT(kOpaque_Alpha == alpha);
                 break;
         }
 
@@ -148,9 +155,10 @@ public:
                 SkASSERT(kOpaque_Alpha != fAlpha);
                 return SkImageInfo::Make(width, height, kN32_SkColorType,
                                          kUnpremul_SkAlphaType, std::move(colorSpace));
-            default:
-                SkASSERT(false);
-                return SkImageInfo::MakeUnknown();
+            case k565_Color:
+                SkASSERT(kOpaque_Alpha == fAlpha);
+                return SkImageInfo::Make(width, height, kRGB_565_SkColorType,
+                                         kOpaque_SkAlphaType, std::move(colorSpace));
         }
     }
 
@@ -169,6 +177,7 @@ public:
             case kRGB_Color:
             case kBGR_Color:
             case kYUV_Color:
+            case k565_Color:
                 return 3 * fBitsPerComponent;
             case kRGBA_Color:
             case kBGRA_Color: