Moved the aec_rdft*.c files to be built using C++

webrtc/modules/audio_processing/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/arm.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("../../build/webrtc.gni")
 
 declare_args() {
   # Outputs some low-level debug files.
   aec_debug_dump = false
 
   # Disables the usual mode where we trust the reported system delay
   # values the AEC receives. The corresponding define is set appropriately
   # in the code, but it can be force-enabled here for testing.
   aec_untrusted_delay_for_testing = false
 }
 
 source_set("audio_processing") {
   sources = [
     "aec/aec_core.cc",
     "aec/aec_core.h",
     "aec/aec_core_internal.h",
-    "aec/aec_rdft.c",
+    "aec/aec_rdft.cc",
     "aec/aec_rdft.h",
     "aec/aec_resampler.cc",
     "aec/aec_resampler.h",
     "aec/echo_cancellation.cc",
     "aec/echo_cancellation.h",
     "aec/echo_cancellation_internal.h",
     "aecm/aecm_core.cc",
     "aecm/aecm_core.h",
     "aecm/echo_control_mobile.cc",
     "aecm/echo_control_mobile.h",
@@ skipping 154 matching lines @@
 
   if (rtc_build_with_neon) {
     deps += [ ":audio_processing_neon" ]
   }
 
   if (current_cpu == "mipsel") {
     sources += [ "aecm/aecm_core_mips.cc" ]
     if (mips_float_abi == "hard") {
       sources += [
         "aec/aec_core_mips.cc",
-        "aec/aec_rdft_mips.c",
+        "aec/aec_rdft_mips.cc",
       ]
     }
   } else {
     sources += [ "aecm/aecm_core_c.cc" ]
   }
 
   if (is_win) {
     cflags = [
       # TODO(jschuh): Bug 1348: fix this warning.
       "/wd4267",  # size_t to int truncations
@@ skipping 20 matching lines @@
     ]
 
     proto_out_dir = "webrtc/modules/audio_processing"
   }
 }
 
 if (current_cpu == "x86" || current_cpu == "x64") {
   source_set("audio_processing_sse2") {
     sources = [
       "aec/aec_core_sse2.cc",
-      "aec/aec_rdft_sse2.c",
+      "aec/aec_rdft_sse2.cc",
     ]
 
     if (is_posix) {
       cflags = [ "-msse2" ]
     }
 
     configs += [ "../..:common_config" ]
     public_configs = [ "../..:common_inherited_config" ]
   }
 }
 
 if (rtc_build_with_neon) {
   source_set("audio_processing_neon") {
     sources = [
       "aec/aec_core_neon.cc",
-      "aec/aec_rdft_neon.c",
+      "aec/aec_rdft_neon.cc",
       "aecm/aecm_core_neon.cc",
       "ns/nsx_core_neon.c",
     ]
 
     if (current_cpu != "arm64") {
       # Enable compilation for the NEON instruction set. This is needed
       # since //build/config/arm.gni only enables NEON for iOS, not Android.
       # This provides the same functionality as webrtc/build/arm_neon.gypi.
       configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags = [ "-mfpu=neon" ]
     }
 
     # Disable LTO on NEON targets due to compiler bug.
     # TODO(fdegans): Enable this. See crbug.com/408997.
     if (rtc_use_lto) {
       cflags -= [
         "-flto",
         "-ffat-lto-objects",
       ]
     }
 
     configs += [ "../..:common_config" ]
     public_configs = [ "../..:common_inherited_config" ]
 
     deps = [
       "../../common_audio",
     ]
   }
 }