Fix GATT client leakage when scan is throttled (1/2)

Currently, scan throttling happens after client is registered, but
before the scan is started. This might lead to scan client being leaked.
This patch fixed that by moving check before client registration.

Bug: 64887233
Test: manual
Change-Id: I22ae624a0c51110cb69679f796926e3b2b36d0ac
Merged-In: I22ae624a0c51110cb69679f796926e3b2b36d0ac
(cherry picked from commit ee02e1ce77)

core/java/android/bluetooth/le/BluetoothLeScanner.java

@@ -344,6 +344,7 @@ public final class BluetoothLeScanner {
         private List<List<ResultStorageDescriptor>> mResultStorages;
 
         // mLeHandle 0: not registered
+        // -2: registration failed because app is scanning to frequently
         // -1: scan stopped or registration failed
         // > 0: registered and scan started
         private int mScannerId;
@@ -364,7 +365,7 @@ public final class BluetoothLeScanner {
         public void startRegistration() {
             synchronized (this) {
                 // Scan stopped.
-                if (mScannerId == -1) return;
+                if (mScannerId == -1 || mScannerId == -2) return;
                 try {
                     mBluetoothGatt.registerScanner(this, mWorkSource);
                     wait(REGISTRATION_CALLBACK_TIMEOUT_MILLIS);
@@ -378,6 +379,10 @@ public final class BluetoothLeScanner {
                     // Registration timed out or got exception, reset scannerId to -1 so no
                     // subsequent operations can proceed.
                     if (mScannerId == 0) mScannerId = -1;
+
+                    // If scanning too frequently, don't report anything to the app.
+                    if (mScannerId == -2) return;
+
                     postCallbackError(mScanCallback,
                             ScanCallback.SCAN_FAILED_APPLICATION_REGISTRATION_FAILED);
                 }
@@ -437,6 +442,9 @@ public final class BluetoothLeScanner {
                         Log.e(TAG, "fail to start le scan: " + e);
                         mScannerId = -1;
                     }
+                } else if (status == ScanCallback.SCAN_FAILED_SCANNING_TOO_FREQUENTLY) {
+                    // applicaiton was scanning too frequently
+                    mScannerId = -2;
                 } else {
                     // registration failed
                     mScannerId = -1;

core/java/android/bluetooth/le/ScanCallback.java

@@ -50,6 +50,12 @@ public abstract class ScanCallback {
      */
     public static final int SCAN_FAILED_OUT_OF_HARDWARE_RESOURCES = 5;
 
+    /**
+     * Fails to start scan as application tries to scan too frequently.
+     * @hide
+     */
+    public static final int SCAN_FAILED_SCANNING_TOO_FREQUENTLY = 6;
+
     static final int NO_ERROR = 0;
 
     /**