Add the backchannel for Blobs to be received into Blink from the database backend.

Source/modules/indexeddb/IDBCursor.cpp

Index: Source/modules/indexeddb/IDBCursor.cpp
diff --git a/Source/modules/indexeddb/IDBCursor.cpp b/Source/modules/indexeddb/IDBCursor.cpp
index 1b8a2a486b4f557450a3c23b0b8af0b1f0e96ae2..13865bdf11d9086efd4d35f47197a8353d951030 100644
--- a/Source/modules/indexeddb/IDBCursor.cpp
+++ b/Source/modules/indexeddb/IDBCursor.cpp
@@ -38,6 +38,7 @@
 #include "modules/indexeddb/IDBTracing.h"
 #include "modules/indexeddb/IDBTransaction.h"
 #include "modules/indexeddb/WebIDBCallbacksImpl.h"
+#include "public/platform/WebBlobInfo.h"
 #include "public/platform/WebIDBDatabase.h"
 #include "public/platform/WebIDBKeyRange.h"
 #include <limits>
@@ -96,6 +97,7 @@ IDBCursor::IDBCursor(PassOwnPtr<blink::WebIDBCursor> backend, WebIDBCursor::Dire
 
 IDBCursor::~IDBCursor()
 {
+    handleBlobAcks();
 }
 
 PassRefPtr<IDBRequest> IDBCursor::update(ScriptState* state, ScriptValue& value, ExceptionState& exceptionState)
@@ -328,16 +330,18 @@ ScriptValue IDBCursor::value(NewScriptState* scriptState)
     const IDBObjectStoreMetadata& metadata = objectStore->metadata();
     RefPtr<IDBAny> value;
     if (metadata.autoIncrement && !metadata.keyPath.isNull()) {
-        value = IDBAny::create(m_value, m_primaryKey, metadata.keyPath);
+        value = IDBAny::create(m_value, m_blobInfo.get(), m_primaryKey, metadata.keyPath);
 #ifndef NDEBUG
-        assertPrimaryKeyValidOrInjectable(scriptState, m_value, m_primaryKey, metadata.keyPath);
+        assertPrimaryKeyValidOrInjectable(scriptState, m_value, m_blobInfo.get(), m_primaryKey, metadata.keyPath);
 #endif
     } else {
-        value = IDBAny::create(m_value);
+        value = IDBAny::create(m_value, m_blobInfo.get());
     }
 
     m_valueDirty = false;
-    return idbAnyToScriptValue(scriptState, value);
+    ScriptValue scriptValue = idbAnyToScriptValue(scriptState, value);
+    handleBlobAcks();
+    return scriptValue;
 }
 
 ScriptValue IDBCursor::source(NewScriptState* scriptState) const
@@ -345,7 +349,7 @@ ScriptValue IDBCursor::source(NewScriptState* scriptState) const
     return idbAnyToScriptValue(scriptState, m_source);
 }
 
-void IDBCursor::setValueReady(PassRefPtr<IDBKey> key, PassRefPtr<IDBKey> primaryKey, PassRefPtr<SharedBuffer> value)
+void IDBCursor::setValueReady(PassRefPtr<IDBKey> key, PassRefPtr<IDBKey> primaryKey, PassRefPtr<SharedBuffer> value, PassOwnPtr<Vector<blink::WebBlobInfo> > blobInfo)
 {
     m_key = key;
     m_keyDirty = true;
@@ -355,6 +359,7 @@ void IDBCursor::setValueReady(PassRefPtr<IDBKey> key, PassRefPtr<IDBKey> primary
 
     if (isCursorWithValue()) {
         m_value = value;
+        m_blobInfo = blobInfo;
         m_valueDirty = true;
     }
 
@@ -376,6 +381,14 @@ bool IDBCursor::isDeleted() const
     return m_source->idbIndex()->isDeleted();
 }
 
+void IDBCursor::handleBlobAcks()
+{
+    if (m_blobInfo.get() && m_blobInfo->size()) {
+        m_request->ackReceivedBlobs(m_blobInfo.get());

[jsbell, 2014/04/15 18:29:07]

I think m_request could be null if called from destructor. This is often racy
since either the cursor's or request's script wrapper could get GC'd last, which
lets the cursor+request break a ref cycle. If the cursor goes first then
m_request is cleared - see checkForReferenceCycle().

(We should probably have a unit test for that.)

[ericu, 2014/04/16 23:04:14]

Good point; in that case, we'd not only crash, we'd also leak.  I've added a
handleBlobAcks to anywhere we clear m_request, and put an ASSERT here.
For which?

[jsbell, 2014/04/17 19:00:33]

For the reference cycle breaking - although oilpan should make it moot.

+        m_blobInfo.clear();
+    }
+}
+
 WebIDBCursor::Direction IDBCursor::stringToDirection(const String& directionString, ExceptionState& exceptionState)
 {
     if (directionString.isNull() || directionString == IDBCursor::directionNext())