Collect host of Web Component usage to send to RAPPOR

Source/core/frame/UseByOriginCounter.cpp

Index: Source/core/frame/UseByOriginCounter.cpp
diff --git a/Source/core/frame/UseByOriginCounter.cpp b/Source/core/frame/UseByOriginCounter.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6be2da0b66a2e0c7ec2ffd0c4e4f4f42b61ad69f
--- /dev/null
+++ b/Source/core/frame/UseByOriginCounter.cpp
@@ -0,0 +1,86 @@
+// Copyright 2015 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 "config.h"
+#include "core/frame/UseByOriginCounter.h"
+
+#include "bindings/core/v8/ScriptState.h"
+#include "core/dom/Document.h"
+#include "public/platform/Platform.h"
+
+namespace blink {
+
+UseByOriginCounter::~UseByOriginCounter()
+{
+    updateMeasurementsAndClear();
+}
+
+UseByOriginCounter::Value::Value()
+    : m_countBits(0)
+{
+}
+
+void UseByOriginCounter::count(const ScriptState* scriptState, Document& document, Feature feature)
+{
+    if (!scriptState || !scriptState->world().isMainWorld())
+        return;
+    document.useByOriginCounterValue().count(feature);
+}
+
+void UseByOriginCounter::Value::count(Feature feature)
+{
+    ASSERT((unsigned)feature >= 0 && feature < Feature::NumberOfFeatures);

[tkent, 2015/03/16 00:30:19]

We don't use C-style cast.  (unsigned) -> static_cast<unsigned>.
Anyway, casting to unsigned and checking >=0 makes no sense.  unsigned is always
>=0.

We shouldn't add multiple assertions in one ASSERT:
  ASSERT(A  && B);  should be:
  ASSERT(A);
  ASSERT(B);

[kojii, 2015/03/16 03:52:51]

Done.

+    m_countBits |= 1 << (unsigned)feature;
+}
+
+void UseByOriginCounter::documentDetached(Document& document)
+{
+    UseByOriginCounter::Value counter = document.useByOriginCounterValue();
+    if (counter.isEmpty())
+        return;
+
+    const KURL& url = document.url();
+    if (!url.protocolIsInHTTPFamily())
+        return;
+
+    m_originAndValues.append(std::make_pair(url.host(), counter));
+    document.useByOriginCounterValue().clear();
+    ASSERT(document.useByOriginCounterValue().isEmpty());
+}
+
+void UseByOriginCounter::updateMeasurementsAndClear()
+{
+    if (m_originAndValues.isEmpty())
+        return;
+
+    // Aggregate values by origins.
+    HashMap<String, UseByOriginCounter::Value> aggregatedByOrigin;
+    for (std::pair<String, UseByOriginCounter::Value>& originAndValue : m_originAndValues) {

[tkent, 2015/03/16 00:30:19]

nit: You can use |const auto&| here.

[kojii, 2015/03/16 03:52:51]

Done.

+        ASSERT(!originAndValue.first.isEmpty());
+        auto result = aggregatedByOrigin.add(originAndValue.first, originAndValue.second);
+        if (!result.isNewEntry)
+            result.storedValue->value.aggregate(originAndValue.second);
+    }
+
+    // Report to RAPPOR.
+    for (auto& originAndValue : aggregatedByOrigin)
+        originAndValue.value.updateMeasurements(originAndValue.key);
+
+    m_originAndValues.clear();
+}
+
+void UseByOriginCounter::Value::aggregate(UseByOriginCounter::Value other)
+{
+    m_countBits |= other.m_countBits;
+}
+
+void UseByOriginCounter::Value::updateMeasurements(const String& origin)
+{
+    if (get(Feature::ElementCreateShadowRoot))
+        Platform::current()->recordRappor("WebComponents.ElementCreateShadowRoot", origin);
+    if (get(Feature::DocumentRegisterElement))
+        Platform::current()->recordRappor("WebComponents.DocumentRegisterElement", origin);
+}
+
+} // namespace blink