Use UMA to track characteristics of dst color spaces

As far as I can tell, SRGB gamma and 2.2 gamma dst color
spaces are very common, with all other possibilities
being extremely rare.

We'd like to limit our color correct implementations
to approximations of SRGB and 2Dot2 destinations:
(1) Allows software and gpu to stay in sync.
(2) Avoids code bloat caused by supporting any
    arbitrary representation that can be packed into an
    ICC profile.

To be confident in making this decision, we need some
metrics to help verify our assumptions about the dst color
spaces.

BUG=

Review-Url: https://codereview.chromium.org/2177933002
Cr-Commit-Position: refs/heads/master@{#407675}

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

@@ -30,4 +30,22 @@ void BitmapImageMetrics::countImageOrientation(const ImageOrientationEnum orient
     orientationHistogram.count(orientation);
 }
 
+void BitmapImageMetrics::countGamma(SkColorSpace* colorSpace)
+{
+    DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, gammaNamedHistogram, new EnumerationHistogram("Blink.ColorSpace.Destination", GammaEnd));
+
+    if (colorSpace) {
+        SkColorSpace::GammaNamed skGamma = colorSpace->gammaNamed();
+        Gamma gamma =
+            (SkColorSpace::kLinear_GammaNamed == skGamma)      ? GammaLinear :
+            (SkColorSpace::kSRGB_GammaNamed == skGamma)        ? GammaSRGB :
+            (SkColorSpace::k2Dot2Curve_GammaNamed == skGamma)  ? Gamma2Dot2 :
+            (SkColorSpace::kNonStandard_GammaNamed == skGamma) ? GammaNonStandard :
+            GammaFail;
+        gammaNamedHistogram.count(gamma);
+    } else {
+        gammaNamedHistogram.count(GammaNull);
+    }
+}
+
 } // namespace blink

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

@@ -7,6 +7,7 @@
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/ImageOrientation.h"
+#include "third_party/skia/include/core/SkColorSpace.h"
 #include "wtf/Allocator.h"
 #include "wtf/Forward.h"
 
@@ -27,8 +28,21 @@ public:
         DecodedImageTypeEnumEnd = ImageBMP + 1
     };
 
+    enum Gamma {
+        // Values synced with 'Gamma' in src/tools/metrics/histograms/histograms.xml
+        GammaLinear = 0,
+        GammaSRGB = 1,
+        Gamma2Dot2 = 2,
+        GammaNonStandard = 3,
+        GammaEmpty = 4,
+        GammaNull = 5,
+        GammaFail = 6,
+        GammaEnd = GammaFail + 1,
+    };
+
     static void countDecodedImageType(const String& type);
     static void countImageOrientation(const ImageOrientationEnum);
+    static void countGamma(SkColorSpace*);
 };
 
 } // namespace blink

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp

@@ -21,6 +21,7 @@
 #include "platform/image-decoders/ImageDecoder.h"
 
 #include "platform/PlatformInstrumentation.h"
+#include "platform/graphics/BitmapImageMetrics.h"
 #include "platform/image-decoders/bmp/BMPImageDecoder.h"
 #include "platform/image-decoders/gif/GIFImageDecoder.h"
 #include "platform/image-decoders/ico/ICOImageDecoder.h"
@@ -331,6 +332,11 @@ void ImageDecoder::setTargetColorProfile(const WebVector<char>& profile)
     if (gTargetColorProfile)
         return;
 
+    {
+        sk_sp<SkColorSpace> colorSpace = SkColorSpace::NewICC(profile.data(), profile.size());
+        BitmapImageMetrics::countGamma(colorSpace.get());
+    }
+
     // FIXME: Add optional ICCv4 support and support for multiple monitors.
     gTargetColorProfile = qcms_profile_from_memory(profile.data(), profile.size());
     if (!gTargetColorProfile)

tools/metrics/histograms/histograms.xml

@@ -3670,6 +3670,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time spent on 2D canvas toDataURL API call.</summary>
 </histogram>
 
+<histogram name="Blink.ColorSpace.Destination" enum="Gamma">
+  <owner>msarett@chromium.org</owner>
+  <summary>Gamma properties of destination color space.</summary>
+</histogram>
+
 <histogram name="Blink.Compositing.UpdateTime" units="microseconds">
   <owner>paint-dev@chromium.org</owner>
   <summary>
@@ -78269,6 +78274,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="8" label="Overflow"/>
 </enum>
 
+<enum name="Gamma" type="int">
+  <int value="0" label="kLinear_Gamma"/>
+  <int value="1" label="kSRGB_Gamma"/>
+  <int value="2" label="k2Dot2Curve_Gamma"/>
+  <int value="3" label="kNonStandard_Gamma"/>
+  <int value="4" label="kNull_Gamma"/>
+  <int value="5" label="kFail_Gamma"/>
+</enum>
+
 <enum name="GATTCharacteristicHash" type="int">
 <!-- Hash values can be produced using tool: bluetooth_metrics_hash (Only built via GN, not GYP) -->