Fix bugs in SkBmpCodec

src/codec/SkBmpStandardCodec.cpp

Index: src/codec/SkBmpStandardCodec.cpp
diff --git a/src/codec/SkBmpStandardCodec.cpp b/src/codec/SkBmpStandardCodec.cpp
index e73d55ebba500bc2b39279bb7dbc89bbbf1a72be..203e7da654568c0de1e8e33e427e96a41fd64ca4 100644
--- a/src/codec/SkBmpStandardCodec.cpp
+++ b/src/codec/SkBmpStandardCodec.cpp
@@ -67,7 +67,7 @@ SkCodec::Result SkBmpStandardCodec::onGetPixels(const SkImageInfo& dstInfo,
 /*
  * Process the color table for the bmp input
  */
- bool SkBmpStandardCodec::createColorTable(SkAlphaType alphaType, int* numColors) {
+ bool SkBmpStandardCodec::createColorTable(SkAlphaType dstAlphaType, int* numColors) {
     // Allocate memory for color table
     uint32_t colorBytes = 0;
     SkPMColor colorTable[256];
@@ -94,21 +94,11 @@ SkCodec::Result SkBmpStandardCodec::onGetPixels(const SkImageInfo& dstInfo,
 
         // Choose the proper packing function
         SkPMColor (*packARGB) (uint32_t, uint32_t, uint32_t, uint32_t);
-        switch (alphaType) {
-            case kOpaque_SkAlphaType:
-            case kUnpremul_SkAlphaType:
-                packARGB = &SkPackARGB32NoCheck;
-                break;
-            case kPremul_SkAlphaType:
-                packARGB = &SkPreMultiplyARGB;
-                break;
-            default:
-                // This should not be reached because conversion possible
-                // should fail if the alpha type is not one of the above
-                // values.
-                SkASSERT(false);
-                packARGB = nullptr;
-                break;
+        SkAlphaType encodedAlphaType = this->getInfo().alphaType();
+        if (kOpaque_SkAlphaType == encodedAlphaType || kUnpremul_SkAlphaType == dstAlphaType) {
+            packARGB = &SkPackARGB32NoCheck;
+        } else {
+            packARGB = &SkPremultiplyARGBInline;
         }
 
         // Fill in the color table
@@ -118,7 +108,7 @@ SkCodec::Result SkBmpStandardCodec::onGetPixels(const SkImageInfo& dstInfo,
             uint8_t green = get_byte(cBuffer.get(), i*fBytesPerColor + 1);
             uint8_t red = get_byte(cBuffer.get(), i*fBytesPerColor + 2);
             uint8_t alpha;
-            if (kOpaque_SkAlphaType == alphaType) {
+            if (kOpaque_SkAlphaType == encodedAlphaType) {
                 alpha = 0xFF;
             } else {
                 alpha = get_byte(cBuffer.get(), i*fBytesPerColor + 3);