InputDevice warning fixes and make warnigs into Error

use const char * for string literals in InputDevice
Remove unused variable in Keyboard

Bug: 35993509
Test: mm in frameworks/native/libs/input builds without the warning
Change-Id: I11242835eae855386c47e56d6c36e5a2f912a28f
diff --git a/libs/input/Android.bp b/libs/input/Android.bp
index 9485d5b..9294419 100644
--- a/libs/input/Android.bp
+++ b/libs/input/Android.bp
@@ -17,7 +17,11 @@
 cc_library {
     name: "libinput",
     host_supported: true,
-
+    cflags: [
+        "-Wall",
+        "-Wextra",
+        "-Werror",
+    ],
     srcs: [
         "Input.cpp",
         "InputDevice.cpp",
diff --git a/libs/input/InputDevice.cpp b/libs/input/InputDevice.cpp
index 9d761fd..4287abe 100644
--- a/libs/input/InputDevice.cpp
+++ b/libs/input/InputDevice.cpp
@@ -90,7 +90,7 @@
     String8 path;
 
     // Treblized input device config files will be located /odm/usr or /vendor/usr.
-    char *rootsForPartition[] {"/odm", "/vendor", getenv("ANDROID_ROOT")};
+    const char *rootsForPartition[] {"/odm", "/vendor", getenv("ANDROID_ROOT")};
     for (size_t i = 0; i < size(rootsForPartition); i++) {
         path.setTo(rootsForPartition[i]);
         path.append("/usr/");
diff --git a/libs/input/Keyboard.cpp b/libs/input/Keyboard.cpp
index 9a01395..07f2289 100644
--- a/libs/input/Keyboard.cpp
+++ b/libs/input/Keyboard.cpp
@@ -208,7 +208,6 @@
 }
 
 int32_t updateMetaState(int32_t keyCode, bool down, int32_t oldMetaState) {
-    int32_t mask;
     switch (keyCode) {
     case AKEYCODE_ALT_LEFT:
         return setEphemeralMetaState(AMETA_ALT_LEFT_ON, down, oldMetaState);