Fix compilation issue detected by internal tool.

Explicit initialization of const member of new EchoCanceller 3
submodule.

Same thing as f3e84717 from https://codereview.webrtc.org/2715573003,
but more of it.

This should be the last one.

TBR=henrik.lundin@webrtc.org

NOTRY=True
BUG=webrtc:6018

Review-Url: https://codereview.webrtc.org/2708373005
Cr-Commit-Position: refs/heads/master@{#16804}

webrtc/modules/audio_processing/aec3/echo_remover.cc

@@ -97,7 +97,8 @@ class EchoRemoverImpl final : public EchoRemover {
 int EchoRemoverImpl::instance_count_ = 0;
 
 EchoRemoverImpl::EchoRemoverImpl(int sample_rate_hz)
-    : data_dumper_(
+    : fft_(),
+      data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
       optimization_(DetectOptimization()),
       sample_rate_hz_(sample_rate_hz),

webrtc/modules/audio_processing/aec3/subtractor.cc

@@ -47,7 +47,8 @@ std::vector<size_t> Subtractor::NumBlocksInRenderSums() const {
 
 Subtractor::Subtractor(ApmDataDumper* data_dumper,
                        Aec3Optimization optimization)
-    : data_dumper_(data_dumper),
+    : fft_(),
+      data_dumper_(data_dumper),
       optimization_(optimization),
       main_filter_(kMainFilterSizePartitions, true, optimization, data_dumper_),
       shadow_filter_(kShadowFilterSizePartitions,

webrtc/modules/audio_processing/aec3/suppression_filter.cc

@@ -60,6 +60,7 @@ const float kSqrtHanning[kFftLength] = {
 
 SuppressionFilter::SuppressionFilter(int sample_rate_hz)
     : sample_rate_hz_(sample_rate_hz),
+      fft_(),
       e_output_old_(NumBandsForRate(sample_rate_hz_)) {
   RTC_DCHECK(ValidFullBandRate(sample_rate_hz_));
   e_input_old_.fill(0.f);