Factor DRP PreviewsState logic out of content

components/data_reduction_proxy/content/renderer/content_previews_render_frame_observer.cc

+// Copyright 2017 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/data_reduction_proxy/content/renderer/content_previews_render_frame_observer.h"
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
+#include "content/public/renderer/render_frame.h"
+#include "third_party/WebKit/public/platform/WebString.h"
+#include "third_party/WebKit/public/web/WebDataSource.h"
+#include "third_party/WebKit/public/web/WebLocalFrame.h"
+
+namespace data_reduction_proxy {
+
+namespace {
+
+bool HasEmptyImageDirective(const blink::WebURLResponse& web_url_response) {

[dougarnett, 2017/06/30 21:03:36]

Bummer that git didn't identify the move of this code. Does git have it own
hinting mechanism (like git5 hint)?

[megjablon, 2017/07/06 19:15:00]

I couldn't find a sure way to do this.

+  std::string chrome_proxy_value =
+      web_url_response
+          .HttpHeaderField(blink::WebString::FromUTF8(chrome_proxy_header()))
+          .Utf8();
+  for (const auto& directive :
+       base::SplitStringPiece(chrome_proxy_value, ",", base::TRIM_WHITESPACE,
+                              base::SPLIT_WANT_NONEMPTY)) {
+    if (!base::StartsWith(directive, page_policies_directive(),
+                          base::CompareCase::INSENSITIVE_ASCII)) {
+      continue;
+    }
+
+    // Check policy directive for empty-image entry.
+    base::StringPiece page_policies_value = base::StringPiece(directive).substr(
+        strlen(page_policies_directive()) + 1);
+    for (const auto& policy :
+         base::SplitStringPiece(page_policies_value, "|", base::TRIM_WHITESPACE,
+                                base::SPLIT_WANT_NONEMPTY)) {
+      if (base::LowerCaseEqualsASCII(policy, empty_image_directive())) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+ContentPreviewsRenderFrameObserver::ContentPreviewsRenderFrameObserver(
+    content::RenderFrame* render_frame)
+    : content::RenderFrameObserver(render_frame) {}
+
+ContentPreviewsRenderFrameObserver::~ContentPreviewsRenderFrameObserver() =
+    default;
+
+content::PreviewsState
+ContentPreviewsRenderFrameObserver::GetPreviewsStateFromResponse(
+    content::PreviewsState original_state,
+    const blink::WebURLResponse& web_url_response) {
+  if (original_state == content::PREVIEWS_UNSPECIFIED) {
+    return content::PREVIEWS_OFF;
+  }
+
+  // Don't update the state if server previews were not enabled.
+  if (!(original_state & content::SERVER_LITE_PAGE_ON)) {
+    return original_state;
+  }
+
+  // At this point, this is a proxy main frame response for which the
+  // PreviewsState needs to be updated from what was enabled/accepted by the
+  // client to what the client should actually do based on the server response.
+
+  content::PreviewsState updated_state = original_state;
+
+  // Clear the Lite Page bit if Lite Page transformation did not occur.
+  if (web_url_response

[dougarnett, 2017/06/30 21:03:36]

Consider adding TODO to leverage common code in drp_headers (eg, adapt
ParseResponseTransform if can work out how to deal with different http header
object types).

[megjablon, 2017/07/06 19:15:00]

Can I put this TODO on you?

+          .HttpHeaderField(blink::WebString::FromUTF8(
+              chrome_proxy_content_transform_header()))
+          .Utf8() != lite_page_directive()) {
+    updated_state &= ~(content::SERVER_LITE_PAGE_ON);
+  }
+
+  // Determine whether to keep or clear Lo-Fi bits. We need to receive the
+  // empty-image policy directive and have SERVER_LOFI_ON in order to retain
+  // Lo-Fi bits.
+  if (!(original_state & content::SERVER_LOFI_ON)) {
+    // Server Lo-Fi not enabled so ensure Client Lo-Fi off for this request.
+    updated_state &= ~(content::CLIENT_LOFI_ON);
+  } else if (!HasEmptyImageDirective(web_url_response)) {
+    updated_state &= ~(content::SERVER_LOFI_ON | content::CLIENT_LOFI_ON);
+  }
+
+  // If we are left with no previews bits set, return the off state.
+  if (updated_state == content::PREVIEWS_UNSPECIFIED) {
+    return content::PREVIEWS_OFF;
+  }
+
+  return updated_state;
+}
+
+void ContentPreviewsRenderFrameObserver::OnDestruct() {
+  delete this;
+}
+
+void ContentPreviewsRenderFrameObserver::DidCommitProvisionalLoad(
+    bool is_new_navigation,
+    bool is_same_document_navigation) {
+  if (is_same_document_navigation)
+    return;
+
+  content::PreviewsState original_state = render_frame()->GetPreviewsState();
+  const blink::WebURLResponse& web_url_response =
+      render_frame()->GetWebFrame()->DataSource()->GetResponse();
+
+  render_frame()->SetPreviewsState(
+      GetPreviewsStateFromResponse(original_state, web_url_response));
+}
+
+}  // namespace data_reduction_proxy