Remove gflags dependency for event_log_visualizer and activity_metric

This is the first step towards getting rid of gflags as a dependency.
It has been causing us extra work for a long time since it's not present
in Chromium as one example.

BUG=webrtc:7644
NOTRY=True

Review-Url: https://codereview.webrtc.org/2874403003
Cr-Commit-Position: refs/heads/master@{#18157}
diff --git a/webrtc/tools/event_log_visualizer/main.cc b/webrtc/tools/event_log_visualizer/main.cc
index 2f5ecd6..b9edd99 100644
--- a/webrtc/tools/event_log_visualizer/main.cc
+++ b/webrtc/tools/event_log_visualizer/main.cc
@@ -10,7 +10,7 @@
 
 #include <iostream>
 
-#include "gflags/gflags.h"
+#include "webrtc/base/flags.h"
 #include "webrtc/logging/rtc_event_log/rtc_event_log_parser.h"
 #include "webrtc/test/field_trial.h"
 #include "webrtc/tools/event_log_visualizer/analyzer.h"
@@ -84,6 +84,7 @@
     "E.g. running with --force_fieldtrials=WebRTC-FooFeature/Enabled/"
     " will assign the group Enabled to field trial WebRTC-FooFeature. Multiple "
     "trials are separated by \"/\"");
+DEFINE_bool(help, false, "prints this message");
 
 int main(int argc, char* argv[]) {
   std::string program_name = argv[0];
@@ -92,16 +93,19 @@
       "Example usage:\n" +
       program_name + " <logfile> | python\n" + "Run " + program_name +
       " --help for a list of command line options\n";
-  google::SetUsageMessage(usage);
-  google::ParseCommandLineFlags(&argc, &argv, true);
-
-  if (argc != 2) {
-    // Print usage information.
-    std::cout << google::ProgramUsage();
+  rtc::FlagList::SetFlagsFromCommandLine(&argc, argv, true);
+  if (FLAG_help) {
+    rtc::FlagList::Print(nullptr, false);
     return 0;
   }
 
-  webrtc::test::InitFieldTrialsFromString(FLAGS_force_fieldtrials);
+  if (argc != 2) {
+    // Print usage information.
+    std::cout << usage;
+    return 0;
+  }
+
+  webrtc::test::InitFieldTrialsFromString(FLAG_force_fieldtrials);
 
   std::string filename = argv[1];
 
@@ -118,15 +122,15 @@
   std::unique_ptr<webrtc::plotting::PlotCollection> collection(
       new webrtc::plotting::PythonPlotCollection());
 
-  if (FLAGS_plot_all || FLAGS_plot_packets) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_packets) {
+    if (FLAG_incoming) {
       analyzer.CreatePacketGraph(webrtc::PacketDirection::kIncomingPacket,
                                  collection->AppendNewPlot());
       analyzer.CreateAccumulatedPacketsGraph(
           webrtc::PacketDirection::kIncomingPacket,
           collection->AppendNewPlot());
     }
-    if (FLAGS_outgoing) {
+    if (FLAG_outgoing) {
       analyzer.CreatePacketGraph(webrtc::PacketDirection::kOutgoingPacket,
                                  collection->AppendNewPlot());
       analyzer.CreateAccumulatedPacketsGraph(
@@ -135,95 +139,95 @@
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_audio_playout) {
+  if (FLAG_plot_all || FLAG_plot_audio_playout) {
     analyzer.CreatePlayoutGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_audio_level) {
+  if (FLAG_plot_all || FLAG_plot_audio_level) {
     analyzer.CreateAudioLevelGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_sequence_number) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_sequence_number) {
+    if (FLAG_incoming) {
       analyzer.CreateSequenceNumberGraph(collection->AppendNewPlot());
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_delay_change) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_delay_change) {
+    if (FLAG_incoming) {
       analyzer.CreateDelayChangeGraph(collection->AppendNewPlot());
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_accumulated_delay_change) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_accumulated_delay_change) {
+    if (FLAG_incoming) {
       analyzer.CreateAccumulatedDelayChangeGraph(collection->AppendNewPlot());
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_fraction_loss) {
+  if (FLAG_plot_all || FLAG_plot_fraction_loss) {
     analyzer.CreateFractionLossGraph(collection->AppendNewPlot());
     analyzer.CreateIncomingPacketLossGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_total_bitrate) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_total_bitrate) {
+    if (FLAG_incoming) {
       analyzer.CreateTotalBitrateGraph(webrtc::PacketDirection::kIncomingPacket,
                                        collection->AppendNewPlot());
     }
-    if (FLAGS_outgoing) {
+    if (FLAG_outgoing) {
       analyzer.CreateTotalBitrateGraph(webrtc::PacketDirection::kOutgoingPacket,
                                        collection->AppendNewPlot());
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_stream_bitrate) {
-    if (FLAGS_incoming) {
+  if (FLAG_plot_all || FLAG_plot_stream_bitrate) {
+    if (FLAG_incoming) {
       analyzer.CreateStreamBitrateGraph(
           webrtc::PacketDirection::kIncomingPacket,
           collection->AppendNewPlot());
     }
-    if (FLAGS_outgoing) {
+    if (FLAG_outgoing) {
       analyzer.CreateStreamBitrateGraph(
           webrtc::PacketDirection::kOutgoingPacket,
           collection->AppendNewPlot());
     }
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_bwe) {
+  if (FLAG_plot_all || FLAG_plot_bwe) {
     analyzer.CreateBweSimulationGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_network_delay_feedback) {
+  if (FLAG_plot_all || FLAG_plot_network_delay_feedback) {
     analyzer.CreateNetworkDelayFeedbackGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_plot_timestamps) {
+  if (FLAG_plot_all || FLAG_plot_timestamps) {
     analyzer.CreateTimestampGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_bitrate_bps) {
+  if (FLAG_plot_all || FLAG_audio_encoder_bitrate_bps) {
     analyzer.CreateAudioEncoderTargetBitrateGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_frame_length_ms) {
+  if (FLAG_plot_all || FLAG_audio_encoder_frame_length_ms) {
     analyzer.CreateAudioEncoderFrameLengthGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_uplink_packet_loss_fraction) {
+  if (FLAG_plot_all || FLAG_audio_encoder_uplink_packet_loss_fraction) {
     analyzer.CreateAudioEncoderUplinkPacketLossFractionGraph(
         collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_fec) {
+  if (FLAG_plot_all || FLAG_audio_encoder_fec) {
     analyzer.CreateAudioEncoderEnableFecGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_dtx) {
+  if (FLAG_plot_all || FLAG_audio_encoder_dtx) {
     analyzer.CreateAudioEncoderEnableDtxGraph(collection->AppendNewPlot());
   }
 
-  if (FLAGS_plot_all || FLAGS_audio_encoder_num_channels) {
+  if (FLAG_plot_all || FLAG_audio_encoder_num_channels) {
     analyzer.CreateAudioEncoderNumChannelsGraph(collection->AppendNewPlot());
   }