Using fully qualified #include paths in isac code.

WebRTC internal code should always used include paths that starts
from the root of the project and that clearly identify the header file.

This allows 'gn check' to actually keep dependencies under control
because 'gn check' cannot enforce anything if the include path
is not fully qualified (starting from the root of the project).

Bug: webrtc:8815
Change-Id: I23fb4fed0c27a4d98bea360315b959af843587bc
Reviewed-on: https://webrtc-review.googlesource.com/46101
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21847}
diff --git a/modules/audio_coding/BUILD.gn b/modules/audio_coding/BUILD.gn
index 8cb659f..e3a077a 100644
--- a/modules/audio_coding/BUILD.gn
+++ b/modules/audio_coding/BUILD.gn
@@ -623,14 +623,18 @@
 rtc_source_set("isac_fix_common") {
   sources = [
     "codecs/isac/fix/source/codec.h",
+    "codecs/isac/fix/source/entropy_coding.h",
     "codecs/isac/fix/source/fft.c",
     "codecs/isac/fix/source/fft.h",
     "codecs/isac/fix/source/filterbank_internal.h",
     "codecs/isac/fix/source/settings.h",
+    "codecs/isac/fix/source/structs.h",
   ]
   public_configs = [ ":isac_fix_config" ]
   deps = [
+    ":isac_common",
     "../..:typedefs",
+    "../../common_audio",
   ]
 }
 
@@ -663,7 +667,6 @@
     "codecs/isac/fix/source/decode_plc.c",
     "codecs/isac/fix/source/encode.c",
     "codecs/isac/fix/source/entropy_coding.c",
-    "codecs/isac/fix/source/entropy_coding.h",
     "codecs/isac/fix/source/filterbank_tables.c",
     "codecs/isac/fix/source/filterbank_tables.h",
     "codecs/isac/fix/source/filterbanks.c",
@@ -688,7 +691,6 @@
     "codecs/isac/fix/source/pitch_lag_tables.h",
     "codecs/isac/fix/source/spectrum_ar_model_tables.c",
     "codecs/isac/fix/source/spectrum_ar_model_tables.h",
-    "codecs/isac/fix/source/structs.h",
     "codecs/isac/fix/source/transform.c",
     "codecs/isac/fix/source/transform_tables.c",
   ]
@@ -2013,6 +2015,7 @@
     deps = [
       ":isac",
       ":isac_test_util",
+      "../../common_audio",
     ]
 
     include_dirs = [