Finish supporting decoding opaque to non-opaque

src/codec/SkWbmpCodec.cpp

Index: src/codec/SkWbmpCodec.cpp
diff --git a/src/codec/SkWbmpCodec.cpp b/src/codec/SkWbmpCodec.cpp
index 527565f6ab4484152f78909583b60400cacfccff..326fc2206a082b6d6bd6d897d8f4cce12c11c1fd 100644
--- a/src/codec/SkWbmpCodec.cpp
+++ b/src/codec/SkWbmpCodec.cpp
@@ -30,15 +30,14 @@ static inline void setup_color_table(SkColorType colorType,
     }
 }
 
-static inline bool valid_color_type(SkColorType colorType, SkAlphaType alphaType) {
+static inline bool valid_color_type(SkColorType colorType) {
     switch (colorType) {
         case kRGBA_8888_SkColorType:
         case kBGRA_8888_SkColorType:
         case kIndex_8_SkColorType:
-            return true;
         case kGray_8_SkColorType:
         case kRGB_565_SkColorType:
-            return kOpaque_SkAlphaType == alphaType;
+            return true;
         default:
             return false;
     }
@@ -128,7 +127,7 @@ SkCodec::Result SkWbmpCodec::onGetPixels(const SkImageInfo& info,
         return kUnimplemented;
     }
 
-    if (!valid_color_type(info.colorType(), info.alphaType()) ||
+    if (!valid_color_type(info.colorType()) ||
             !valid_alpha(info.alphaType(), this->getInfo().alphaType())) {
         return kInvalidConversion;
     }
@@ -196,7 +195,7 @@ SkCodec::Result SkWbmpCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
         return kUnimplemented;
     }
 
-    if (!valid_color_type(dstInfo.colorType(), dstInfo.alphaType()) ||
+    if (!valid_color_type(dstInfo.colorType()) ||
             !valid_alpha(dstInfo.alphaType(), this->getInfo().alphaType())) {
         return kInvalidConversion;
     }