Pepper: Fix renderer crash on plugin destruction.

components/nacl/renderer/ppb_nacl_private_impl.cc

Index: components/nacl/renderer/ppb_nacl_private_impl.cc
diff --git a/components/nacl/renderer/ppb_nacl_private_impl.cc b/components/nacl/renderer/ppb_nacl_private_impl.cc
index 5c7b9f980b7700c0f4a599ccce6f61e333b45985..9b94422daf0f2027bbd89eeec80831a0908357c3 100644
--- a/components/nacl/renderer/ppb_nacl_private_impl.cc
+++ b/components/nacl/renderer/ppb_nacl_private_impl.cc
@@ -1602,6 +1602,11 @@ class PexeDownloader : public blink::WebURLLoaderClient {
   virtual void didGetNexeFd(int32_t pp_error,
                             bool cache_hit,
                             PP_FileHandle file_handle) {
+    if (!content::PepperPluginInstance::Get(instance_)) {
+      delete this;
+      return;
+    }
+
     HistogramEnumerate("NaCl.Perf.PNaClCache.IsHit", cache_hit, 2);
     if (cache_hit) {
       stream_handler_->DidCacheHit(stream_handler_user_data_, file_handle);
@@ -1623,17 +1628,21 @@ class PexeDownloader : public blink::WebURLLoaderClient {
                               const char* data,
                               int data_length,
                               int encoded_data_length) {
-    // Stream the data we received to the stream callback.
-    stream_handler_->DidStreamData(stream_handler_user_data_,
-                                   data,
-                                   data_length);
+    if (content::PepperPluginInstance::Get(instance_)) {
+      // Stream the data we received to the stream callback.
+      stream_handler_->DidStreamData(stream_handler_user_data_,
+                                     data,
+                                     data_length);
+    }
   }
 
   virtual void didFinishLoading(blink::WebURLLoader* loader,
                                 double finish_time,
                                 int64_t total_encoded_data_length) {
     int32_t result = success_ ? PP_OK : PP_ERROR_FAILED;
-    stream_handler_->DidFinishStream(stream_handler_user_data_, result);
+
+    if (content::PepperPluginInstance::Get(instance_))
+      stream_handler_->DidFinishStream(stream_handler_user_data_, result);
     delete this;
   }