Factor DocumentSubresourceFilter out of SubresourceFilterAgent.

components/subresource_filter/content/renderer/document_subresource_filter.cc

Index: components/subresource_filter/content/renderer/document_subresource_filter.cc
diff --git a/components/subresource_filter/content/renderer/document_subresource_filter.cc b/components/subresource_filter/content/renderer/document_subresource_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3b55625b516e1dd53389ba301214e10e3dee32da
--- /dev/null
+++ b/components/subresource_filter/content/renderer/document_subresource_filter.cc
@@ -0,0 +1,53 @@
+// Copyright 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 "components/subresource_filter/content/renderer/document_subresource_filter.h"
+
+#include <climits>
+
+#include "base/logging.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "components/subresource_filter/core/common/memory_mapped_ruleset.h"
+#include "third_party/WebKit/public/platform/WebURL.h"
+#include "url/gurl.h"
+
+namespace subresource_filter {
+
+DocumentSubresourceFilter::DocumentSubresourceFilter(
+    ActivationState activation_state,
+    const scoped_refptr<const MemoryMappedRuleset>& ruleset,
+    std::vector<GURL> /* ignored_ancestor_document_urls */)
+    : activation_state_(activation_state), ruleset_(ruleset) {
+  DCHECK_NE(activation_state_, ActivationState::DISABLED);
+  DCHECK(ruleset);
+}
+
+DocumentSubresourceFilter::~DocumentSubresourceFilter() = default;
+
+bool DocumentSubresourceFilter::allowLoad(
+    const blink::WebURL& resourceUrl,
+    blink::WebURLRequest::RequestContext /* ignored */) {
+  ++num_loads_evaluated_;
+  if (DoesLoadMatchFilteringRules(GURL(resourceUrl))) {
+    ++num_loads_matching_rules_;
+    if (activation_state_ == ActivationState::ENABLED) {
+      ++num_loads_disallowed_;
+      return false;
+    }
+  }
+  return true;
+}
+
+bool DocumentSubresourceFilter::DoesLoadMatchFilteringRules(
+    const GURL& resource_url) {
+  static_assert(CHAR_BIT == 8, "Assumed char was 8 bits.");
+  base::StringPiece disallowed_suffix = base::StringPiece(
+      reinterpret_cast<const char*>(ruleset_->data()), ruleset_->length());
+  return !disallowed_suffix.empty() &&
+         base::EndsWith(resource_url.path_piece(), disallowed_suffix,
+                        base::CompareCase::SENSITIVE);
+}
+
+}  // namespace subresource_filter