Use -Werror in frameworks/native/libs/vr

* Suppress/fix warnings of unused variable, parameter,
  private-field, and function.
* Fix warnings about typedef missing declarator.
* Use -Wno-error to keep existing warnings, to fix later.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Ifb82fcd76fcb5d9c9d9f017f2541581661493bd5
diff --git a/services/vr/hardware_composer/Android.bp b/services/vr/hardware_composer/Android.bp
index 5cb201d..88a5a611 100644
--- a/services/vr/hardware_composer/Android.bp
+++ b/services/vr/hardware_composer/Android.bp
@@ -43,6 +43,11 @@
 
   cflags: [
     "-DLOG_TAG=\"vr_hwc\"",
+    "-Wall",
+    "-Werror",
+    "-Wno-error=sign-compare",  // fix later
+    "-Wno-unused-private-field",
+    "-Wno-unused-parameter",
   ],
 
 }
@@ -56,6 +61,7 @@
     "aidl/android/dvr/parcelable_composer_layer.cpp",
     "aidl/android/dvr/parcelable_unique_fd.cpp",
   ],
+  cflags: ["-Wall", "-Werror"],
   aidl: {
     include_dirs: ["frameworks/native/services/vr/hardware_composer/aidl"],
     export_aidl_headers: true,
@@ -91,6 +97,8 @@
   ],
   cflags: [
     "-DLOG_TAG=\"vr_hwc\"",
+    "-Wall",
+    "-Werror",
   ],
 }
 
@@ -119,6 +127,8 @@
   ],
   cflags: [
     "-DLOG_TAG=\"vr_hwc\"",
+    "-Wall",
+    "-Werror",
   ],
   init_rc: [
     "vr_hwc.rc",
@@ -129,6 +139,12 @@
   name: "vr_hwc_test",
   gtest: true,
   srcs: ["tests/vr_composer_test.cpp"],
+  cflags: [
+    "-Wall",
+    "-Werror",
+    "-Wno-error=sign-compare",  // fix later
+    "-Wno-unused-parameter",
+  ],
   static_libs: [
     "libgtest",
     "libvr_hwc-impl",