Adding test to ensure context restoration due to GC doesn't crash

content/test/data/gpu/webgl.html

Index: content/test/data/gpu/webgl.html
diff --git a/content/test/data/gpu/webgl.html b/content/test/data/gpu/webgl.html
index 001c569a0f457b979187f97d3bfab811261d58d1..fc444d94ab9078a9714993b8f1fe6dacf3cf72b7 100644
--- a/content/test/data/gpu/webgl.html
+++ b/content/test/data/gpu/webgl.html
@@ -59,6 +59,35 @@ function testContextRestored() {
     window.domAutomationController.send("FAILED");
 }
 
+function testQuantityLoss() {
+  var count = 0;
+  var iterations = 128;
+
+  function createAndDiscardContext() {
+    count++;
+
+    var c = document.createElement("canvas");
+    c.width = 1;
+    c.height = 1;
+
+    var ctx = c.getContext("experimental-webgl");
+    if (!ctx) {
+      return false;
+    }
+    ctx.clear(gl.COLOR_BUFFER_BIT);
+
+    if (count < iterations) {
+      window.requestAnimationFrame(createAndDiscardContext);
+    } else {
+      window.domAutomationController.setAutomationId(1);
+      alreadySetAutomationId = true;
+      window.domAutomationController.send("LOADED");
+    }
+  };
+
+  createAndDiscardContext();
+}
+
 function contextLostTest(kind)
 {
   switch (kind) {
@@ -79,6 +108,12 @@ function contextLostTest(kind)
       alreadySetAutomationId = true;
       window.domAutomationController.send("LOADED");
       break;
+    case "forced_quantity_loss":
+      // Test creates many new contexts, forcing the original context to be
+      // lost. Then a garbage collect is triggered and the original context is
+      // watched to ensure it restores properly.
+      testQuantityLoss();
+      break;
   }
 }