Prepare to test all image decode modes to F16

I've only been running F16 tests in "colorImage" mode.
We really should be running our "image" tests to F16 as well - so
they can be tested with scaling, subsets, etc.

This CL fixes bugs so that we can enable those tests.

BUG=skia:

Change-Id: I8137eb4fce7ea12f2c9d233a029d946d4a63e6b0
Reviewed-on: https://skia-review.googlesource.com/7801
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index cea87f7..ae34f90 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -364,6 +364,13 @@
                     kOpaque_SkAlphaType != decodeInfo->alphaType()) {
                 return false;
             }
+
+            if (kRGBA_F16_SkColorType == canvasColorType) {
+                sk_sp<SkColorSpace> linearSpace =
+                        as_CSB(decodeInfo->colorSpace())->makeLinearGamma();
+                *decodeInfo = decodeInfo->makeColorSpace(std::move(linearSpace));
+            }
+
             *decodeInfo = decodeInfo->makeColorType(canvasColorType);
             break;
     }