UMA histogram to measure the time OTS takes to decode a webfont

Source/platform/fonts/opentype/OpenTypeSanitizer.cpp

Index: Source/platform/fonts/opentype/OpenTypeSanitizer.cpp
diff --git a/Source/platform/fonts/opentype/OpenTypeSanitizer.cpp b/Source/platform/fonts/opentype/OpenTypeSanitizer.cpp
index d17f9f9b3adb0e7bc8134749a64ebaaca4a651db..90500b7cac1ebde94f3b7731b1e4c97c73d33621 100644
--- a/Source/platform/fonts/opentype/OpenTypeSanitizer.cpp
+++ b/Source/platform/fonts/opentype/OpenTypeSanitizer.cpp
@@ -31,12 +31,32 @@
 #include "config.h"
 #include "platform/fonts/opentype/OpenTypeSanitizer.h"
 
-#include "platform/SharedBuffer.h"
 #include "opentype-sanitiser.h"
 #include "ots-memory-stream.h"
+#include "platform/SharedBuffer.h"
+#include "public/platform/Platform.h"
+#include "wtf/CurrentTime.h"
 
 namespace blink {
 
+static void recordDecodeSpeedHistogram(SharedBuffer* buffer, double decodeTime, size_t decodedSize)
+{
+    if (decodeTime <= 0)
+        return;
+
+    const char* histogramName = "WebFont.DecodeSpeed.SFNT";
+    if (buffer->size() >= 4) {
+        const char* data = buffer->data();
+        if (data[0] == 'w' && data[1] == 'O' && data[2] == 'F' && data[3] == 'F')
+            histogramName = "WebFont.DecodeSpeed.WOFF";
+        else if (data[0] == 'w' && data[1] == 'O' && data[2] == 'F' && data[3] == '2')
+            histogramName = "WebFont.DecodeSpeed.WOFF2";
+    }
+
+    double kbPerSecond = decodedSize / (1000 * decodeTime);
+    blink::Platform::current()->histogramCustomCounts(histogramName, kbPerSecond, 0, 500000, 50);
+}
+
 PassRefPtr<SharedBuffer> OpenTypeSanitizer::sanitize()
 {
     if (!m_buffer)
@@ -57,10 +77,12 @@ PassRefPtr<SharedBuffer> OpenTypeSanitizer::sanitize()
     // much larger than the original.
 
     ots::ExpandingMemoryStream output(m_buffer->size(), maxWebFontSize);
+    double start = currentTime();
     if (!ots::Process(&output, reinterpret_cast<const uint8_t*>(m_buffer->data()), m_buffer->size()))
         return nullptr;
 
     const size_t transcodeLen = output.Tell();
+    recordDecodeSpeedHistogram(m_buffer, currentTime() - start, transcodeLen);
     return SharedBuffer::create(static_cast<unsigned char*>(output.get()), transcodeLen);
 }