Revert "Add memory metric to trace event to investigate omnibox performance"

This reverts commit e1b21dc7.

Reason for revert:
  1) No longer needed
  2) Slowing down omnibox

Original change's description:
> Add memory metric to trace event to investigate omnibox performance
>
> Adding estimated memory usage to the quick history provider.
> it is suspected to be slow and cause jank on UI thread when memory usage
> is high.
>
> These metrics will be received with slow-reports and will help to
> investigate some jank on UI thread.
>
> R=​mpearson@chromium.org
>
> Bug: 868419
> Change-Id: I344f84ec00f318fdb9db63c5b464b119a9d5e3eb
> Reviewed-on: https://chromium-review.googlesource.com/1156847
> Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
> Reviewed-by: Mark Pearson <mpearson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#579919}

TBR=mpearson@chromium.org,etienneb@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 868419
Change-Id: I96785874209368579844e9c55052bc53de12a5a8
Reviewed-on: https://chromium-review.googlesource.com/1174692Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582973}

components/omnibox/browser/history_quick_provider.cc

@@ -45,13 +45,7 @@ HistoryQuickProvider::HistoryQuickProvider(AutocompleteProviderClient* client)
 
 void HistoryQuickProvider::Start(const AutocompleteInput& input,
                                  bool minimal_changes) {
-  // TODO(etienneb): Remove metrics when https://crbug/868419 is closed.
-  size_t memory_usage = 0;
-  if (in_memory_url_index_)
-    memory_usage = in_memory_url_index_->EstimateMemoryUsage();
-  TRACE_EVENT2("omnibox", "HistoryQuickProvider::Start",
-               "memory_url_index_.memory_usage", memory_usage, "text_length",
-               input.text().length());
+  TRACE_EVENT0("omnibox", "HistoryQuickProvider::Start");
   matches_.clear();
   if (disabled_ || input.from_omnibox_focus())
     return;

components/omnibox/browser/in_memory_url_index.cc

@@ -123,18 +123,6 @@ void InMemoryURLIndex::Init() {
   PostRestoreFromCacheFileTask();
 }
 
-size_t InMemoryURLIndex::EstimateMemoryUsage() const {
-  size_t res = 0;
-
-  res += base::trace_event::EstimateMemoryUsage(scheme_whitelist_);
-
-  // TODO(dyaroshev): Add support for scoped_refptr in
-  //                  base::trace_event::EstimateMemoryUsage.
-  res += sizeof(URLIndexPrivateData) + private_data_->EstimateMemoryUsage();
-
-  return res;
-}
-
 void InMemoryURLIndex::ClearPrivateData() {
   private_data_->Clear();
 }
@@ -227,7 +215,14 @@ void InMemoryURLIndex::OnHistoryServiceLoaded(
 bool InMemoryURLIndex::OnMemoryDump(
     const base::trace_event::MemoryDumpArgs& args,
     base::trace_event::ProcessMemoryDump* process_memory_dump) {
-  size_t res = EstimateMemoryUsage();
+  size_t res = 0;
+
+  res += base::trace_event::EstimateMemoryUsage(scheme_whitelist_);
+
+  // TODO(dyaroshev): Add support for scoped_refptr in
+  //                  base::trace_event::EstimateMemoryUsage.
+  res += sizeof(URLIndexPrivateData) + private_data_->EstimateMemoryUsage();
+
   const std::string dump_name =
       base::StringPrintf("omnibox/in_memory_url_index/0x%" PRIXPTR,
                          reinterpret_cast<uintptr_t>(this));

components/omnibox/browser/in_memory_url_index.h

@@ -115,9 +115,6 @@ class InMemoryURLIndex : public KeyedService,
   // history database.
   void Init();
 
-  // Estimates the amount of memory used.
-  size_t EstimateMemoryUsage() const;
-
   // Scans the history index and returns a vector with all scored, matching
   // history items. This entry point simply forwards the call on to the
   // URLIndexPrivateData class. For a complete description of this function