Revert "Remove code from obsolete field trial from 2015."

This reverts commit 55424d2f.

Reason for revert: Windows compile failure.

Original change's description:
> Remove code from obsolete field trial from 2015.
> 
> Originally added here: https://codereview.chromium.org/1117193004
> 
> Bug: 799180
> Change-Id: I8e46beafdc57c249fb9909e39c197519b2652c7b
> Reviewed-on: https://chromium-review.googlesource.com/902769
> Reviewed-by: Mark Mentovai <mark@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#534776}

TBR=asvitkine@chromium.org,mark@chromium.org

Change-Id: If512ffd90d5218190d3bddb4931491f76e161aed
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 799180
Reviewed-on: https://chromium-review.googlesource.com/905462Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534781}

base/sys_info.cc

@@ -7,6 +7,9 @@
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
+#include "base/metrics/field_trial.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "base/sys_info_internal.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
@@ -61,6 +64,14 @@ static LazyInstance<
 
 // static
 bool SysInfo::IsLowEndDevice() {
+  const std::string group_name =
+      base::FieldTrialList::FindFullName("MemoryReduction");
+
+  // Low End Device Mode will be enabled if this client is assigned to
+  // one of those EnabledXXX groups.
+  if (StartsWith(group_name, "Enabled", CompareCase::SENSITIVE))
+    return true;
+
   return g_lazy_low_end_device.Get().value();
 }
 #endif