color: Clarify default behaviors

ui/gfx/color_transform.cc

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/color_transform.h"
 
 #include <algorithm>
 #include <cmath>
 #include <list>
 #include <memory>
@@ skipping 255 matching lines @@
       step->Transform(colors, num);
   }
   size_t NumberOfStepsForTesting() const override { return steps_.size(); }
 
  private:
   void AppendColorSpaceToColorSpaceTransform(ColorSpace from,
                                              const ColorSpace& to,
                                              ColorTransform::Intent intent);
   void Simplify();
 
+  // Retrieve the ICC profile from which |color_space| was created, only if that
+  // is a more precise representation of the color space than the primaries and
+  // transfer function in |color_space|.
+  ScopedQcmsProfile GetQCMSProfileIfNecessary(const ColorSpace& color_space);
+
   std::list<std::unique_ptr<ColorTransformStep>> steps_;
 };
 
 class ColorTransformNull : public ColorTransformStep {
  public:
   ColorTransformNull* GetNull() override { return this; }
   bool IsNull() override { return true; }
   void Transform(ColorTransform::TriStim* color, size_t num) override {}
 };
 
@@ skipping 357 matching lines @@
     qcms_chain_transform(from_.get(), to_.get(),
                          reinterpret_cast<float*>(colors),
                          reinterpret_cast<float*>(colors), num * 3);
   }
 
  private:
   ScopedQcmsProfile from_;
   ScopedQcmsProfile to_;
 };
 
-ScopedQcmsProfile GetQCMSProfileIfAvailable(const ColorSpace& color_space) {
-  ICCProfile icc_profile = ICCProfile::FromColorSpace(color_space);
-  if (icc_profile.GetData().empty())
+ScopedQcmsProfile ColorTransformInternal::GetQCMSProfileIfNecessary(
+    const ColorSpace& color_space) {
+  ICCProfile icc_profile;
+  if (!ICCProfile::FromId(color_space.icc_profile_id_, true, &icc_profile))
     return nullptr;
   return ScopedQcmsProfile(qcms_profile_from_memory(
       icc_profile.GetData().data(), icc_profile.GetData().size()));
 }
 
 ScopedQcmsProfile GetXYZD50Profile() {
   // QCMS is trixy, it has a datatype called qcms_CIE_xyY, but what it expects
   // is in fact not xyY color coordinates, it just wants the x/y values of the
   // primaries with Y equal to 1.0.
   qcms_CIE_xyYTRIPLE xyz;
   qcms_CIE_xyY w;
   xyz.red.x = 1.0f;
   xyz.red.y = 0.0f;
   xyz.red.Y = 1.0f;
   xyz.green.x = 0.0f;
   xyz.green.y = 1.0f;
   xyz.green.Y = 1.0f;
   xyz.blue.x = 0.0f;
   xyz.blue.y = 0.0f;
   xyz.blue.Y = 1.0f;
   w.x = 0.34567f;
   w.y = 0.35850f;
   w.Y = 1.0f;
   return ScopedQcmsProfile(qcms_profile_create_rgb_with_gamma(w, xyz, 1.0f));
 }
 
 ColorTransformInternal::ColorTransformInternal(const ColorSpace& from,
                                                const ColorSpace& to,
                                                Intent intent) {
-  ScopedQcmsProfile from_profile = GetQCMSProfileIfAvailable(from);
-  ScopedQcmsProfile to_profile = GetQCMSProfileIfAvailable(to);
+  ScopedQcmsProfile from_profile = GetQCMSProfileIfNecessary(from);
+  ScopedQcmsProfile to_profile = GetQCMSProfileIfNecessary(to);
   bool has_from_profile = !!from_profile;
   bool has_to_profile = !!to_profile;
 
   if (from_profile) {
     steps_.push_back(base::MakeUnique<QCMSColorTransform>(
         std::move(from_profile), GetXYZD50Profile()));
   }
 
   AppendColorSpaceToColorSpaceTransform(
       has_from_profile ? ColorSpace::CreateXYZD50() : from,
@@ skipping 42 matching lines @@
 // static
 std::unique_ptr<ColorTransform> ColorTransform::NewColorTransform(
     const ColorSpace& from,
     const ColorSpace& to,
     Intent intent) {
   return std::unique_ptr<ColorTransform>(
       new ColorTransformInternal(from, to, intent));
 }
 
 }  // namespace gfx