Remove unnecessary include and dependency in ui/latency/mojo

gn check --check-generated reported a missing build
dependency and this fixes that. An example of a reported error is:

ERROR at //out/Default/gen/ui/latency/mojo/latency_info.mojom-forward.h:44:11: Can't include this header from here.
          ^----------------------
The target:
  //ui/latency/mojo:interfaces
is including a file from the target:
  //ipc:ipc

Since the header isn't actually used, the simple fix is to remove it, though that revealed some
other code that was missing includes of their own.

Bug: 938893
Change-Id: I8e2648d5e681ee9640282eab31028a102cdc96eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1550467Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Auto-Submit: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#653575}

components/ui_devtools/viz/viz_devtools_unittest.cc

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/containers/flat_map.h"
+#include "base/strings/stringprintf.h"
+#include "base/unguessable_token.h"
 #include "components/ui_devtools/css_agent.h"
 #include "components/ui_devtools/ui_devtools_unittest_utils.h"
 #include "components/ui_devtools/ui_element.h"

components/viz/service/compositor_frame_fuzzer/fuzzer_software_display_provider.cc

@@ -9,6 +9,9 @@
 #include <vector>
 
 #include "base/files/file_util.h"
+#include "base/optional.h"
+#include "base/strings/stringprintf.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "components/viz/service/display/software_output_device.h"
 #include "components/viz/service/display_embedder/software_output_surface.h"
 #include "third_party/skia/include/encode/SkPngEncoder.h"

ui/latency/mojo/latency_info.typemap

@@ -3,10 +3,7 @@
 # found in the LICENSE file.
 
 mojom = "//ui/latency/mojo/latency_info.mojom"
-public_headers = [
-  "//ipc/ipc_message_utils.h",
-  "//ui/latency/latency_info.h",
-]
+public_headers = [ "//ui/latency/latency_info.h" ]
 traits_headers = [ "//ui/latency/mojo/latency_info_struct_traits.h" ]
 sources = [
   "latency_info_struct_traits.cc",