Revert of Remove candidates when doing continual gathering (patchset #15 id:560001 of https://codereview.webrtc.org/1648813004/ )

Reason for revert:
Breaks the build.  Suggest we reland with a default implementation of the new method, update Chrome, land a change that changes |{}| -> |= 0;|

Here's the error:

FAILED: /b/build/goma/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/content/renderer/media/webrtc/test_support_content.mock_peer_connection_dependency_factory.o.d -DV8_DEPRECATION_WARNINGS -DCLD_VERSION=2 -D__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORE=0 -DCHROMIUM_BUILD -DCR_CLANG_REVISION=262839-1 -DUSE_LIBJPEG_TURBO=1 -DENABLE_WEBRTC=1 -DENABLE_MEDIA_ROUTER=1 -DUSE_PROPRIETARY_CODECS -DENABLE_PEPPER_CDMS -DENABLE_CONFIGURATION_POLICY -DENABLE_NOTIFICATIONS -DENABLE_TOPCHROME_MD=1 -DDCHECK_ALWAYS_ON=1 -DFIELDTRIAL_TESTING_ENABLED -DENABLE_TASK_MANAGER=1 -DENABLE_EXTENSIONS=1 -DENABLE_PDF=1 -DENABLE_PLUGIN_INSTALLATION=1 -DENABLE_PLUGINS=1 -DENABLE_SESSION_SERVICE=1 -DENABLE_THEMES=1 -DENABLE_AUTOFILL_DIALOG=1 -DENABLE_PRINTING=1 -DENABLE_BASIC_PRINTING=1 -DENABLE_PRINT_PREVIEW=1 -DENABLE_SPELLCHECK=1 -DUSE_BROWSER_SPELLCHECKER=1 -DENABLE_CAPTIVE_PORTAL_DETECTION=1 -DENABLE_APP_LIST=1 -DENABLE_SETTINGS_APP=1 -DENABLE_SUPERVISED_USERS=1 -DENABLE_SERVICE_DISCOVERY=1 -DV8_USE_EXTERNAL_STARTUP_DATA -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DMOJO_USE_SYSTEM_IMPL -DGTEST_HAS_POSIX_RE=0 -DGTEST_LANG_CXX11=0 -DSK_SUPPORT_GPU=1 -DSK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS -DUNIT_TEST -DGTEST_HAS_RTTI=0 -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_STATIC_IMPLEMENTATION -DPROTOBUF_USE_DLLS -DGOOGLE_PROTOBUF_NO_RTTI -DGOOGLE_PROTOBUF_NO_STATIC_INITIALIZER -DCHROME_PNG_WRITE_SUPPORT -DPNG_USER_CONFIG -DFEATURE_ENABLE_SSL -DFEATURE_ENABLE_VOICEMAIL -DEXPAT_RELATIVE_PATH -DGTEST_RELATIVE_PATH -DNO_MAIN_THREAD_WRAPPING -DNO_SOUND_SYSTEM -DOSX -DWEBRTC_MAC -DWEBRTC_POSIX -DXML_STATIC -DWEBRTC_CHROMIUM_BUILD -DUSE_LIBPCI=1 -DUSE_OPENSSL=1 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -D_FORTIFY_SOURCE=2 -Igen -I../.. -I../../third_party/khronos -I../../gpu -I../../skia/config -Igen/angle -I../../third_party/WebKit/Source -I../../third_party/skia/include/core -I../../third_party/skia/include/effects -I../../third_party/skia/include/pdf -I../../third_party/skia/include/gpu -I../../third_party/skia/include/lazy -I../../third_party/skia/include/pathops -I../../third_party/skia/include/pipe -I../../third_party/skia/include/ports -I../../third_party/skia/include/utils -I../../third_party/skia/include/utils/mac -I../../skia/ext -I../../testing/gmock/include -I../../testing/gtest/include -I../../third_party/icu/source/i18n -I../../third_party/icu/source/common -Igen/ui/resources -Igen/protoc_out -I../../third_party/protobuf -I../../third_party/protobuf/src -I../../third_party/WebKit -I../../ipc -I../../third_party/opus/src/include -I../../third_party/WebKit -I../../third_party/npapi -I../../third_party/npapi/bindings -I../../third_party/libpng -I../../third_party/zlib -I../../third_party/libwebp -I../../third_party/ots/include -I../../third_party/qcms/src -I../../third_party/iccjpeg -I../../third_party/libjpeg_turbo -I../../v8/include -I../../third_party/webrtc_overrides -I../../third_party/libjingle/overrides -I../../third_party/libjingle/source -I../../third_party -I../../third_party/expat/files/lib -I../../third_party/libvpx/source/libvpx -isysroot /Applications/Xcode5.1.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk -O2 -gdwarf-2 -fvisibility=hidden -Werror -mmacosx-version-min=10.6 -arch x86_64 -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wno-selector-type-mismatch -Wpartial-availability -Wheader-hygiene -Wno-char-subscripts -Wno-unneeded-internal-declaration -Wno-covered-switch-default -Wstring-conversion -Wno-c++11-narrowing -Wno-deprecated-register -Wno-inconsistent-missing-override -Wno-shift-negative-value -std=c++11 -stdlib=libc++ -fno-rtti -fno-exceptions -fvisibility-inlines-hidden -fno-threadsafe-statics -Xclang -load -Xclang /b/build/slave/Mac_Builder/build/src/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-templates -Xclang -plugin-arg-find-bad-constructs -Xclang follow-macro-expansion -fcolor-diagnostics -fno-strict-aliasing  -c ../../content/renderer/media/webrtc/mock_peer_connection_dependency_factory.cc -o obj/content/renderer/media/webrtc/test_support_content.mock_peer_connection_dependency_factory.o
../../content/renderer/media/webrtc/mock_peer_connection_dependency_factory.cc:404:14: error: allocating an object of abstract class type 'content::MockSessionDescription'
  return new MockSessionDescription(type, sdp);
             ^
../../third_party/webrtc/api/jsep.h:100:18: note: unimplemented pure virtual method 'RemoveCandidates' in 'MockSessionDescription'
  virtual size_t RemoveCandidates(
                 ^
1 error generated.
ninja: build stopped: subcommand failed.

Original issue's description:
> When doing candidate re-gathering in the same generation, Remove the existing local candidate on the same network
> and signaling the remote side to remove its remote candidate by setting the candidate priority to 0.
>
> BUG=
>
> Committed: https://crrev.com/84430da6817ce69c53bfad088be5c9df8b420f01
> Cr-Commit-Position: refs/heads/master@{#11958}

TBR=pthatcher@webrtc.org,deadbeef@webrtc.org,glaznev@webrtc.org,honghaiz@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.webrtc.org/1785613011

Cr-Commit-Position: refs/heads/master@{#11960}
diff --git a/webrtc/api/webrtcsdp.h b/webrtc/api/webrtcsdp.h
index e7fdb34..2b22b62 100644
--- a/webrtc/api/webrtcsdp.h
+++ b/webrtc/api/webrtcsdp.h
@@ -22,11 +22,8 @@
 
 #include <string>
 
-namespace cricket {
-class Candidate;
-}  // namespace cricket
-
 namespace webrtc {
+
 class IceCandidateInterface;
 class JsepIceCandidate;
 class JsepSessionDescription;
@@ -45,10 +42,6 @@
 // candidate - The candidate to be serialized.
 std::string SdpSerializeCandidate(const IceCandidateInterface& candidate);
 
-// Serializes a cricket Candidate.
-// candidate - The candidate to be serialized.
-std::string SdpSerializeCandidate(const cricket::Candidate& candidate);
-
 // Deserializes the passed in SDP string to a JsepSessionDescription.
 // message - SDP string to be Deserialized.
 // jdesc - The JsepSessionDescription deserialized from the SDP string.
@@ -68,20 +61,6 @@
 bool SdpDeserializeCandidate(const std::string& message,
                              JsepIceCandidate* candidate,
                              SdpParseError* error);
-
-// Deserializes the passed in SDP string to a cricket Candidate.
-// The first line must be a=candidate line and only the first line will be
-// parsed.
-// transport_name - The transport name (MID) of the candidate.
-// message - The SDP string to be deserialized.
-// candidate - The cricket Candidate from the SDP string.
-// error - The detail error information when parsing fails.
-// return - true on success, false on failure.
-bool SdpDeserializeCandidate(const std::string& transport_name,
-                             const std::string& message,
-                             cricket::Candidate* candidate,
-                             SdpParseError* error);
-
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_WEBRTCSDP_H_