Allow index sources to be unpremul.

src/images/SkScaledBitmapSampler.cpp

Index: src/images/SkScaledBitmapSampler.cpp
diff --git a/src/images/SkScaledBitmapSampler.cpp b/src/images/SkScaledBitmapSampler.cpp
index fe425d58b1cab09ac744114a18b8d0184049391a..8bb1bde7c41928d6eeaaff1b534c08624b5e779c 100644
--- a/src/images/SkScaledBitmapSampler.cpp
+++ b/src/images/SkScaledBitmapSampler.cpp
@@ -396,10 +396,9 @@ static bool Sample_Index_D8888_SkipZ(void* SK_RESTRICT dstRow,
 
 static SkScaledBitmapSampler::RowProc
 get_index_to_8888_proc(const SkScaledBitmapSampler::Options& opts) {
-    if (!opts.fPremultiplyAlpha) {
-        // Unpremultiplied is not supported for an index source.
-        return NULL;
-    }
+    // The caller is expected to have created the source colortable
+    // properly with respect to opts.fPremultiplyAlpha, so premul makes
+    // no difference here.
     // Dither makes no difference
     if (opts.fSkipZeros) {
         return Sample_Index_D8888_SkipZ;
@@ -803,7 +802,7 @@ SkScaledBitmapSampler::RowProc gTestProcs[] = {
     Sample_Index_DI,    Sample_Index_DI,        NULL,                       NULL,                       // to Index8
     Sample_Index_D565,  Sample_Index_D565_D,    Sample_Index_D565,          Sample_Index_D565_D,        // to 565
     Sample_Index_D4444, Sample_Index_D4444_D,   NULL,                       NULL,                       // to 4444
-    Sample_Index_D8888, Sample_Index_D8888,     NULL,                       NULL,                       // to 8888
+    Sample_Index_D8888, Sample_Index_D8888,     Sample_Index_D8888,         Sample_Index_D8888,         // to 8888
     // RGB
     NULL,               NULL,                   NULL,                       NULL,                       // to A8
     NULL,               NULL,                   NULL,                       NULL,                       // to Index8