webrtc-apm: Replace deprected Json::Reader call.

Never versions of jsoncpp have deprectated the use of Json::Reader and
replaced it with a factory pattern. This change allows us to uprev
jsoncpp.

No change in functionality.

BUG=b:157880485
TEST=FEATURES=test emerge-betty media-libs/webrtc-apm

Change-Id: I18d12fbd4c7e1a9e5878a7083630c390acce2199
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/webrtc-apm/+/2265532
Tested-by: Stuart Langley <slangley@chromium.org>
Auto-Submit: Stuart Langley <slangley@chromium.org>
Commit-Queue: Hsinyu Chao <hychao@chromium.org>
Reviewed-by: Hsinyu Chao <hychao@chromium.org>

api/audio/echo_canceller3_config_json.cc

diff --git a/api/audio/echo_canceller3_config_json.cc b/api/audio/echo_canceller3_config_json.cc
index 4c8c8ab..02c4d99 100644
--- a/api/audio/echo_canceller3_config_json.cc
+++ b/api/audio/echo_canceller3_config_json.cc
@@ -121,9 +121,16 @@
   *parsing_successful = true;
 
   Json::Value root;
-  bool success = Json::Reader().parse(std::string(json_string), root);
+  Json::CharReaderBuilder builder;
+  std::unique_pre<Json::CharReader> reader(builder.newCharReader());
+  std::string error;
+
+  bool success = reader->parse(json_string.data(),
+                               json_string.data() + json_string.size(),
+                               &root, &error);
   if (!success) {
-    RTC_LOG(LS_ERROR) << "Incorrect JSON format: " << json_string;
+    RTC_LOG(LS_ERROR) << "Incorrect JSON format: " << json_string
+                      << " error: " << error;
     *parsing_successful = false;
     return;
   }