Moved the AEC C code to be built using C++

webrtc/modules/audio_processing/BUILD.gn

Index: webrtc/modules/audio_processing/BUILD.gn
diff --git a/webrtc/modules/audio_processing/BUILD.gn b/webrtc/modules/audio_processing/BUILD.gn
index 58347933e5bd9231ea4840f6e4b4c2c4e6895022..454d1be06a10d64d04a6f20bd514c5b3485cb6ef 100644
--- a/webrtc/modules/audio_processing/BUILD.gn
+++ b/webrtc/modules/audio_processing/BUILD.gn
@@ -22,14 +22,14 @@ declare_args() {
 
 source_set("audio_processing") {
   sources = [
-    "aec/aec_core.c",
+    "aec/aec_core.cc",
     "aec/aec_core.h",
     "aec/aec_core_internal.h",
     "aec/aec_rdft.c",
     "aec/aec_rdft.h",
     "aec/aec_resampler.c",
     "aec/aec_resampler.h",
-    "aec/echo_cancellation.c",
+    "aec/echo_cancellation.cc",
     "aec/echo_cancellation.h",
     "aec/echo_cancellation_internal.h",
     "aecm/aecm_core.c",
@@ -198,7 +198,7 @@ source_set("audio_processing") {
     sources += [ "aecm/aecm_core_mips.c" ]
     if (mips_float_abi == "hard") {
       sources += [
-        "aec/aec_core_mips.c",
+        "aec/aec_core_mips.cc",
         "aec/aec_rdft_mips.c",
       ]
     }
@@ -239,7 +239,7 @@ if (rtc_enable_protobuf) {
 if (current_cpu == "x86" || current_cpu == "x64") {
   source_set("audio_processing_sse2") {
     sources = [
-      "aec/aec_core_sse2.c",
+      "aec/aec_core_sse2.cc",
       "aec/aec_rdft_sse2.c",
     ]
 
@@ -255,7 +255,7 @@ if (current_cpu == "x86" || current_cpu == "x64") {
 if (rtc_build_with_neon) {
   source_set("audio_processing_neon") {
     sources = [
-      "aec/aec_core_neon.c",
+      "aec/aec_core_neon.cc",
       "aec/aec_rdft_neon.c",
       "aecm/aecm_core_neon.c",
       "ns/nsx_core_neon.c",