Revert of Use an explicit identifier in Config (patchset #4 id:60001 of https://codereview.webrtc.org/1538643004/ )

Reason for revert:
Reverting due to problem with roll:

/b/build/slave/linux/build/src/buildtools/linux64/gn gen //out/Release '--args=ffmpeg_branding="Chrome" proprietary_codecs=true is_debug=false is_component_build=false use_goma=true goma_dir="/b/build/goma" symbol_level=1 dcheck_always_on=true' --check --runtime-deps-list-file=/b/build/slave/linux/build/src/out/Release/runtime_deps
  -> returned 1
ERROR at //third_party/webrtc/BUILD.gn:245:18: Item not found
    configs -= [ "//build/config/clang:find_bad_constructs" ]
                 ^-----------------------------------------
You were trying to remove "//build/config/clang:find_bad_constructs"
from the list but it wasn't there.
GN gen failed: 1
step returned non-zero exit code: 1
@@@STEP_FAILURE@@@

Original issue's description:
> Use an explicit identifier in Config
>
> This let's us use them to configure them when using WebRTC as an external library. One use case where this is necessary is in the Android OS.
>
> Committed: https://crrev.com/25249d92d3cf105bcc7b684c8924ccdbc9afcb93
> Cr-Commit-Position: refs/heads/master@{#11231}

TBR=henrik.lundin@webrtc.org,stefan@webrtc.org,tommi@chromium.org,aluebs@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.webrtc.org/1586563003

Cr-Commit-Position: refs/heads/master@{#11239}

talk/libjingle.gyp

@@ -712,16 +712,10 @@
       'include_dirs': [
         '<(DEPTH)/testing/gtest/include',
       ],
-      'include_dirs!': [
-        '<(DEPTH)/webrtc',
-      ],
       'direct_dependent_settings': {
         'include_dirs': [
           '<(DEPTH)/testing/gtest/include',
         ],
-        'include_dirs!': [
-          '<(DEPTH)/webrtc',
-        ],
       },
       'sources': [
         'session/media/audiomonitor.cc',

webrtc/BUILD.gn

@@ -238,12 +238,6 @@ source_set("webrtc_common") {
 
   configs += [ ":common_config" ]
   public_configs = [ ":common_inherited_config" ]
-
-  if (is_clang) {
-    # Suppress warnings from Chrome's Clang plugins.
-    # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
-    configs -= [ "//build/config/clang:find_bad_constructs" ]
-  }
 }
 
 source_set("gtest_prod") {

webrtc/common.h

@@ -17,23 +17,6 @@
 
 namespace webrtc {
 
-// Only add new values to the end of the enumeration and never remove (only
-// deprecate) to maintain binary compatibility.
-enum class ConfigOptionID {
-  kMyExperimentForTest,
-  kAlgo1CostFunctionForTest,
-  kTemporalLayersFactory,
-  kNetEqCapacityConfig,
-  kNetEqFastAccelerate,
-  kVoicePacing,
-  kExtendedFilter,
-  kDelayAgnostic,
-  kExperimentalAgc,
-  kExperimentalNs,
-  kBeamforming,
-  kIntelligibility
-};
-
 // Class Config is designed to ease passing a set of options across webrtc code.
 // Options are identified by typename in order to avoid incorrect casts.
 //
@@ -78,6 +61,8 @@ class Config {
   }
 
  private:
+  typedef void* OptionIdentifier;
+
   struct BaseOption {
     virtual ~BaseOption() {}
   };
@@ -91,9 +76,11 @@ class Config {
     T* value;
   };
 
+  // Own implementation of rtti-subset to avoid depending on rtti and its costs.
   template<typename T>
-  static ConfigOptionID identifier() {
-    return T::identifier;
+  static OptionIdentifier identifier() {
+    static char id_placeholder;
+    return &id_placeholder;
   }
 
   // Used to instantiate a default constructed object that doesn't needs to be
@@ -105,7 +92,7 @@ class Config {
     return def;
   }
 
-  typedef std::map<ConfigOptionID, BaseOption*> OptionMap;
+  typedef std::map<OptionIdentifier, BaseOption*> OptionMap;
   OptionMap options_;
 
   // RTC_DISALLOW_COPY_AND_ASSIGN

webrtc/config.h

@@ -16,7 +16,6 @@
 #include <string>
 #include <vector>
 
-#include "webrtc/common.h"
 #include "webrtc/common_types.h"
 #include "webrtc/typedefs.h"
 
@@ -129,7 +128,6 @@ struct VideoEncoderConfig {
 struct NetEqCapacityConfig {
   NetEqCapacityConfig() : enabled(false), capacity(0) {}
   explicit NetEqCapacityConfig(int value) : enabled(true), capacity(value) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kNetEqCapacityConfig;
   bool enabled;
   int capacity;
 };
@@ -137,14 +135,12 @@ struct NetEqCapacityConfig {
 struct NetEqFastAccelerate {
   NetEqFastAccelerate() : enabled(false) {}
   explicit NetEqFastAccelerate(bool value) : enabled(value) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kNetEqFastAccelerate;
   bool enabled;
 };
 
 struct VoicePacing {
   VoicePacing() : enabled(false) {}
   explicit VoicePacing(bool value) : enabled(value) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kVoicePacing;
   bool enabled;
 };
 

webrtc/modules/audio_processing/include/audio_processing.h

@@ -65,7 +65,6 @@ class VoiceDetection;
 struct ExtendedFilter {
   ExtendedFilter() : enabled(false) {}
   explicit ExtendedFilter(bool enabled) : enabled(enabled) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kExtendedFilter;
   bool enabled;
 };
 
@@ -77,7 +76,6 @@ struct ExtendedFilter {
 struct DelayAgnostic {
   DelayAgnostic() : enabled(false) {}
   explicit DelayAgnostic(bool enabled) : enabled(enabled) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kDelayAgnostic;
   bool enabled;
 };
 
@@ -98,7 +96,6 @@ struct ExperimentalAgc {
       : enabled(enabled), startup_min_volume(kAgcStartupMinVolume) {}
   ExperimentalAgc(bool enabled, int startup_min_volume)
       : enabled(enabled), startup_min_volume(startup_min_volume) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kExperimentalAgc;
   bool enabled;
   int startup_min_volume;
 };
@@ -108,7 +105,6 @@ struct ExperimentalAgc {
 struct ExperimentalNs {
   ExperimentalNs() : enabled(false) {}
   explicit ExperimentalNs(bool enabled) : enabled(enabled) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kExperimentalNs;
   bool enabled;
 };
 
@@ -131,7 +127,6 @@ struct Beamforming {
       : enabled(enabled),
         array_geometry(array_geometry),
         target_direction(target_direction) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kBeamforming;
   const bool enabled;
   const std::vector<Point> array_geometry;
   const SphericalPointf target_direction;
@@ -146,7 +141,6 @@ struct Beamforming {
 struct Intelligibility {
   Intelligibility() : enabled(false) {}
   explicit Intelligibility(bool enabled) : enabled(enabled) {}
-  static const ConfigOptionID identifier = ConfigOptionID::kIntelligibility;
   bool enabled;
 };
 

webrtc/modules/video_coding/codecs/vp8/temporal_layers.h

@@ -14,7 +14,6 @@
 
 #include "vpx/vpx_encoder.h"
 
-#include "webrtc/common.h"
 #include "webrtc/common_video/include/video_image.h"
 #include "webrtc/typedefs.h"
 
@@ -31,8 +30,6 @@ class TemporalLayers {
     virtual ~Factory() {}
     virtual TemporalLayers* Create(int temporal_layers,
                                    uint8_t initial_tl0_pic_idx) const;
-    static const ConfigOptionID identifier =
-        ConfigOptionID::kTemporalLayersFactory;
   };
 
   virtual ~TemporalLayers() {}

webrtc/test/common_unittest.cc

@@ -15,7 +15,6 @@ namespace webrtc {
 namespace {
 
 struct MyExperiment {
-  static const ConfigOptionID identifier = ConfigOptionID::kMyExperimentForTest;
   static const int kDefaultFactor;
   static const int kDefaultOffset;
 
@@ -57,8 +56,6 @@ TEST(Config, SetNullSetsTheOptionBackToDefault) {
 }
 
 struct Algo1_CostFunction {
-  static const ConfigOptionID identifier =
-      ConfigOptionID::kAlgo1CostFunctionForTest;
   Algo1_CostFunction() {}
 
   virtual int cost(int x) const {