Drop support for HDR -> SDR ColorTransforms.

They don't work anymore with SkiaRenderer, have poor power characteristics,
and haven't shown up in the wild. I.e., sites are only serving HDR content
to HDR displays.

This also fixes a compilation error with the SMPTEST2084 shader when not
using GLSL.

BUG=1023671,1015599

Change-Id: I855992d369364beb899dc145c1595d42aef3b5be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913613
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714991}

ui/gfx/color_space.cc

@@ -946,6 +946,7 @@ void ColorSpace::GetRangeAdjustMatrix(SkMatrix44* matrix) const {
 
 bool ColorSpace::ToSkYUVColorSpace(SkYUVColorSpace* out) const {
   if (range_ == RangeID::FULL) {
+    // TODO(dalecurtis): This is probably not right for BT.2020.
     *out = kJPEG_SkYUVColorSpace;
     return true;
   }

ui/gfx/color_transform.cc

@@ -684,7 +684,7 @@ class ColorTransformToLinear : public ColorTransformPerChannelTransferFn {
                   "  float v2 = v;\n"
                   "  #endif\n";
         } else {
-          *src << "  float v2 = v\n";
+          *src << "  " << scalar_type << " v2 = v;\n";
         }
         *src << "  v2 = pow(max(pow(v2, 1.0 / m2) - c1, 0.0) /\n"
                 "              (c2 - c3 * pow(v2, 1.0 / m2)), 1.0 / m1);\n"
@@ -874,32 +874,6 @@ void ColorTransformInternal::AppendColorSpaceToColorSpaceTransform(
     ColorSpace src,
     const ColorSpace& dst,
     ColorTransform::Intent intent) {
-  if (intent == ColorTransform::Intent::INTENT_PERCEPTUAL) {
-    switch (src.transfer_) {
-      case ColorSpace::TransferID::SMPTEST2084:
-        if (!dst.IsHDR()) {
-          // We don't have an HDR display, so replace SMPTE 2084 with
-          // something that returns ranges more or less suitable for a normal
-          // display.
-          src.transfer_ = ColorSpace::TransferID::SMPTEST2084_NON_HDR;
-        }
-        break;
-
-      case ColorSpace::TransferID::ARIB_STD_B67:
-        if (!dst.IsHDR()) {
-          // Interpreting HLG using a gamma 2.4 works reasonably well for SDR
-          // displays.
-          src.transfer_ = ColorSpace::TransferID::GAMMA24;
-        }
-        break;
-
-      default:  // Do nothing
-        break;
-    }
-
-    // TODO(hubbe): shrink gamuts here (never stretch gamuts)
-  }
-
   steps_.push_back(
       std::make_unique<ColorTransformMatrix>(GetRangeAdjustMatrix(src)));