fix [4026375] SensorManager quaternion functions can call sqrt with a negative number [DO NOT MERGE]

Just make sure to clamp the argument to zero.

Bug: 4026375
Change-Id: Idd3d4ef977e87c1b3f6b54371105c3152d7dc6b9

Author: pixelflinger

core/java/android/hardware/SensorManager.java

@@ -2026,8 +2026,8 @@ public static void getQuaternionFromVector(float[] Q, float[] rv) {
         if (rv.length == 4) {
             Q[0] = rv[3];
         } else {
-            //In this case, the w component of the quaternion is known to be a positive number
-            Q[0] = (float)Math.sqrt(1 - rv[0]*rv[0] - rv[1]*rv[1] - rv[2]*rv[2]);
+            Q[0] = 1 - rv[0]*rv[0] - rv[1]*rv[1] - rv[2]*rv[2];
+            Q[0] = (Q[0] > 0) ? (float)Math.sqrt(Q[0]) : 0;
         }
         Q[1] = rv[0];
         Q[2] = rv[1];