Implement a shell of FindRequestManager, and hook it up to WebContentsImpl.

content/browser/find_request_manager.cc

+// 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 "content/browser/find_request_manager.h"
+
+#include "content/browser/frame_host/render_frame_host_impl.h"
+#include "content/browser/web_contents/web_contents_impl.h"
+#include "content/common/frame_messages.h"
+#include "content/common/input_messages.h"
+
+namespace content {
+
+namespace {
+
+// An invalid ID. This value is invalid for any render process ID, render frame
+// ID, or find request ID.
+const int kInvalidId = -1;
+
+}  // namespace
+
+FindRequestManager::FindRequestManager(WebContentsImpl* web_contents)
+    :
+#if defined(OS_ANDROID)
+      match_rects_{kInvalidId},

[ncarter (slow), 2016/04/11 21:27:35]

This is C++11 uniform initialization syntax, which is banned according to
https://chromium-cpp.appspot.com/.

It may be allowed very soon (
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/GF96FshwHLw
).

But even if it were allowed, I think you're better off with just making it so
that the MatchRects struct's default constructor does this initialization, since
you rely on that later in the file. (you can use the C++11 "Non-Static Class
Member Initializers" to do this in the header)

[paulmeyer, 2016/04/12 17:54:25]

Done.

+#endif
+      contents_(web_contents),
+      current_session_id_(kInvalidId),
+      current_request_(),
+      number_of_matches_(0),
+      active_match_ordinal_(0) {}
+
+FindRequestManager::~FindRequestManager() {}
+
+void FindRequestManager::Find(int request_id,
+                              const base::string16& search_text,
+                              const blink::WebFindOptions& options) {
+  // Every find request must have a unique ID, and these IDs must strictly
+  // increase so that newer requests always have greater IDs than older
+  // requests.
+  DCHECK_GT(request_id, current_request_.id);
+  DCHECK_GT(request_id, current_session_id_);
+
+  FindRequest request{request_id, search_text, options};

[lfg, 2016/04/11 20:10:53]

Compared to what you had before, this will cause an extra unnecessary heap
memory allocation because of the string.

[ncarter (slow), 2016/04/11 21:27:35]

Use assignment syntax here, per the "BarStruct" draft rules on
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/GF96FshwHLw/9HytI...

FindRequest request = {request_id, search_text, options};

[paulmeyer, 2016/04/12 17:54:25]

lfg: That won't be the case anymore after subsequent CL, but I'd like to keep it
set
up this way for now.

[paulmeyer, 2016/04/12 17:54:25]

ncarter: Done.

+
+  if (options.findNext) {
+    // This is a find next operation.
+
+    // This implies that there is an ongoing find session with the same search
+    // text.
+    DCHECK_GE(current_session_id_, 0);
+    DCHECK_EQ(request.search_text, current_request_.search_text);
+  } else {
+    // This is an initial find operation.
+    Reset(request);
+  }
+
+  SendFindIPC(request, contents_->GetMainFrame());
+}
+
+void FindRequestManager::StopFinding(StopFindAction action) {
+  SendStopFindingIPC(action, contents_->GetMainFrame());
+  current_session_id_ = kInvalidId;
+}
+
+void FindRequestManager::OnFindReply(RenderFrameHost* rfh,
+                                     int request_id,
+                                     int number_of_matches,
+                                     const gfx::Rect& selection_rect,
+                                     int active_match_ordinal,
+                                     bool final_update) {
+  // Ignore stale replies from abandoned find sessions.
+  if (current_session_id_ == kInvalidId || request_id < current_session_id_)
+    return;
+
+  // Update the stored results.
+  number_of_matches_ = number_of_matches;
+  selection_rect_ = selection_rect;
+  active_match_ordinal_ = active_match_ordinal;
+
+  NotifyFindReply(request_id, final_update);
+}
+
+#if defined(OS_ANDROID)
+void FindRequestManager::ActivateNearestFindResult(float x,
+                                                   float y) {
+  if (current_session_id_ == kInvalidId)
+    return;
+
+  auto rfh = contents_->GetMainFrame();
+  rfh->Send(new InputMsg_ActivateNearestFindResult(
+      rfh->GetRoutingID(), current_session_id_, x, y));
+}
+
+void FindRequestManager::RequestFindMatchRects(int current_version) {
+  match_rects_.request_version = current_version;
+  SendFindMatchRectsIPC(contents_->GetMainFrame());
+}
+
+void FindRequestManager::OnFindMatchRectsReply(
+    RenderFrameHost* rfh,
+    int version,
+    const std::vector<gfx::RectF>& rects,
+    const gfx::RectF& active_rect) {
+  contents_->NotifyFindMatchRectsReply(version, rects, active_rect);
+}
+#endif
+
+void FindRequestManager::Reset(const FindRequest& initial_request) {
+  current_session_id_ = initial_request.id;
+  current_request_ = initial_request;
+  number_of_matches_ = 0;
+  active_match_ordinal_ = 0;
+  selection_rect_ = gfx::Rect();
+#if defined(OS_ANDROID)
+  match_rects_ = FindMatchRectsState();

[ncarter (slow), 2016/04/11 21:27:35]

The default ctor isn't declared, so as far as I can tell this will initialize
match_rects_ to random memory values.

[lfg, 2016/04/11 21:46:42]

We had this discussion offline (I also didn't know about this), but when you add
the brackets () the class is zero-initialized. That said, I would also prefer to
see the constructor.

For reference: http://en.cppreference.com/w/cpp/language/value_initialization

"if T is a class type with a default constructor that is neither user-provided
nor deleted (that is, it may be a class with an implicitly-defined or defaulted
default constructor), the object is zero-initialized and then it is
default-initialized if it has a non-trivial default constructor;"

[paulmeyer, 2016/04/12 17:54:25]

I made the construction explicit now.

[ncarter (slow), 2016/04/12 18:16:35]

Thanks for explaining this (the zero initialization is new with c++11?).

Seems like we still needed a default ctor, since we wanted the member to be
initialized to -1 and not zero.

+#endif
+}
+
+void FindRequestManager::SendFindIPC(FindRequest request,

[lfg, 2016/04/11 20:10:53]

Pass by const reference.

[paulmeyer, 2016/04/12 17:54:25]

Done.

+                                     RenderFrameHost* rfh) {
+  rfh->Send(new FrameMsg_Find(rfh->GetRoutingID(), request.id,
+                              request.search_text, request.options));
+}
+
+void FindRequestManager::SendStopFindingIPC(StopFindAction action,
+                                            RenderFrameHost* rfh) const {
+  rfh->Send(new FrameMsg_StopFinding(rfh->GetRoutingID(), action));
+}
+
+void FindRequestManager::NotifyFindReply(int request_id,
+                                         bool final_update) const {
+  if (request_id == kInvalidId) {
+    NOTREACHED();
+    return;
+  }
+
+  contents_->NotifyFindReply(request_id, number_of_matches_, selection_rect_,
+                             active_match_ordinal_, final_update);
+}
+
+#if defined(OS_ANDROID)
+void FindRequestManager::SendFindMatchRectsIPC(RenderFrameHost* rfh) {
+  rfh->Send(new FrameMsg_FindMatchRects(rfh->GetRoutingID(),
+                                        match_rects_.request_version));
+}
+#endif
+
+}  // namespace content