Delete kInvalid_GammaNamed

This has only ever existed for UMA and is done serving its purpose.

TBR=fmalita@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2310443002
Cr-Commit-Position: refs/heads/master@{#416368}

third_party/WebKit/Source/platform/graphics/BitmapImageMetrics.cpp

@@ -48,9 +48,6 @@ void BitmapImageMetrics::countGamma(SkColorSpace* colorSpace)
         case SkColorSpace::k2Dot2Curve_GammaNamed:
             gamma = Gamma2Dot2;
             break;
-        case SkColorSpace::kInvalid_GammaNamed:
-            gamma = GammaInvalid;
-            break;
         default:
             if (colorSpace->gammasAreMatching()) {
                 if (colorSpace->gammasAreValues()) {