Bug 1923741 - Add telemetry to measure how many users have read only system temporary folders. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D225139

gfx/thebes/gfxPlatform.cpp

@@ -1042,6 +1042,16 @@ void gfxPlatform::Init() {
   }
 }
 
+static bool IsOsTempDirWritable() {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(file));
+  NS_ENSURE_SUCCESS(rv, false);
+  bool writable = false;
+  rv = file->IsWritable(&writable);
+  NS_ENSURE_SUCCESS(rv, false);
+  return writable;
+}
+
 void gfxPlatform::ReportTelemetry() {
   MOZ_RELEASE_ASSERT(XRE_IsParentProcess(),
                      "GFX: Only allowed to be called from parent process.");
@@ -1064,6 +1074,9 @@ void gfxPlatform::ReportTelemetry() {
       supportsHDR |= screen->GetIsHDR();
     }
     Telemetry::ScalarSet(Telemetry::ScalarID::GFX_SUPPORTS_HDR, supportsHDR);
+
+    bool tmpWritable = IsOsTempDirWritable();
+    Telemetry::ScalarSet(Telemetry::ScalarID::GFX_TMP_WRITABLE, tmpWritable);
   }
 
   nsString adapterDesc;

toolkit/components/telemetry/Scalars.yaml

@@ -4030,6 +4030,21 @@ gfx:
     record_in_processes:
       - 'main'
     release_channel_collection: opt-out
+  tmp_writable:
+    bug_numbers:
+      - 1923741
+    description: >
+      Is the system temporary directory writable
+    expires: "134"
+    kind: boolean
+    notification_emails:
+      - gfx-telemetry-alerts@mozilla.com
+      - aosmond@mozilla.com
+    products:
+      - 'firefox'
+    record_in_processes:
+      - 'main'
+    release_channel_collection: opt-out
 
 apz:
   scrollwheel_overshoot: