[core] Update ImageManager.OnStyleImageMissingBeforeSpriteLoaded

So that it checks pending image requests for a different requestor.

test/renderer/image_manager.test.cpp

@@ -189,18 +189,28 @@ TEST(ImageManager, OnStyleImageMissingBeforeSpriteLoaded) {
 
     // Repeated request of the same image shall not result another
     // `ImageManagerObserver.onStyleImageMissing()` call.
-    imageManager.getImages(requestor, std::make_pair(dependencies, imageCorrelationID));
+    imageManager.getImages(requestor, std::make_pair(dependencies, ++imageCorrelationID));
     runLoop.runOnce();
 
     EXPECT_EQ(observer.count, 1);
 
     // Request for updated dependencies must be dispatched to the
     // observer.
     dependencies.emplace("post", ImageType::Icon);
-    imageManager.getImages(requestor, std::make_pair(dependencies, imageCorrelationID));
+    imageManager.getImages(requestor, std::make_pair(dependencies, ++imageCorrelationID));
     runLoop.runOnce();
 
     EXPECT_EQ(observer.count, 2);
+
+    // Another requestor shall not have pending requests for already obtained images.
+    StubImageRequestor anotherRequestor(imageManager);
+    imageManager.getImages(anotherRequestor, std::make_pair(dependencies, ++imageCorrelationID));
+    ASSERT_FALSE(anotherRequestor.hasPendingRequests());
+
+    dependencies.emplace("unfamiliar", ImageType::Icon);
+    imageManager.getImages(anotherRequestor, std::make_pair(dependencies, ++imageCorrelationID));
+    EXPECT_TRUE(anotherRequestor.hasPendingRequests());
+    EXPECT_TRUE(anotherRequestor.hasPendingRequest("unfamiliar"));
 }
 
 TEST(ImageManager, OnStyleImageMissingAfterSpriteLoaded) {