Bug 1905454 - Make sure the consumed data is erased, r=necko-reviewers,valentin

No matter what the consumedCount is, the previous code always erases 1 byte of data, which is not correct. We should ensure that the amount of data removed matches the consumedCount.

Differential Revision: https://phabricator.services.mozilla.com/D218551

netwerk/base/nsIncrementalStreamLoader.cpp

@@ -157,7 +157,8 @@ nsresult nsIncrementalStreamLoader::WriteSegmentFun(
       // Adopting elems back (at least its portion).
       self->mData.replaceRawBuffer(elems, length);
       if (consumedCount > 0) {
-        self->mData.erase(self->mData.begin() + consumedCount);
+        self->mData.erase(self->mData.begin(),
+                          self->mData.begin() + consumedCount);
       }
     }
   }

netwerk/test/unit/test_bug1218029.js

@@ -47,6 +47,13 @@ var tests = [
     consume: [0],
     dataChunks: ["E", "E"],
   },
+  {
+    data: "123456789",
+    chunks: [2, 3, 4],
+    status: Cr.NS_OK,
+    consume: [1, 2, 6],
+    dataChunks: ["12", "2345", "456789", ""],
+  },
 ];
 
 /**