Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

third_party/WebKit/Source/core/dom/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//third_party/WebKit/Source/core/core.gni")
 
 blink_core_sources("dom") {
   split_count = 5
 
   sources = [
     "AXObjectCache.cpp",
     "AXObjectCache.h",
     "AnimationWorkletProxyClient.h",
     "Attr.cpp",
+    "Attr.h",
     "AttributeCollection.h",
     "CDATASection.cpp",
     "CDATASection.h",
     "CSSSelectorWatch.cpp",
+    "CSSSelectorWatch.h",
     "CharacterData.cpp",
     "ChildFrameDisconnector.cpp",
     "ChildFrameDisconnector.h",
     "ChildListMutationScope.cpp",
     "ChildListMutationScope.h",
     "ChildNodeList.cpp",
     "ChildNodeList.h",
     "ClassCollection.cpp",
     "ClassCollection.h",
     "ClientRect.cpp",
     "ClientRect.h",
     "ClientRectList.cpp",
     "ClientRectList.h",
     "CollectionIndexCache.h",
     "Comment.cpp",
     "Comment.h",
     "CompositorProxiedPropertySet.cpp",
     "CompositorProxiedPropertySet.h",
     "CompositorProxy.cpp",
     "CompositorProxy.h",
     "CompositorProxyClient.h",
     "CompositorWorkerProxyClient.cpp",
     "CompositorWorkerProxyClient.h",
     "ContainerNode.cpp",
+    "ContainerNode.h",
     "ContextFeatures.cpp",
     "ContextFeatures.h",
     "ContextLifecycleNotifier.cpp",
     "ContextLifecycleNotifier.h",
     "ContextLifecycleObserver.cpp",
     "ContextLifecycleObserver.h",
     "DOMArrayBuffer.cpp",
     "DOMArrayBuffer.h",
     "DOMArrayBufferBase.h",
     "DOMArrayBufferView.h",
     "DOMArrayPiece.cpp",
     "DOMArrayPiece.h",
     "DOMDataView.cpp",
     "DOMDataView.h",
     "DOMException.cpp",
     "DOMException.h",
     "DOMImplementation.cpp",
+    "DOMImplementation.h",
     "DOMMatrix.cpp",
     "DOMMatrix.h",
     "DOMMatrixReadOnly.cpp",
     "DOMMatrixReadOnly.h",
     "DOMNodeIds.cpp",
     "DOMNodeIds.h",
     "DOMPoint.cpp",
     "DOMPoint.h",
     "DOMPointReadOnly.cpp",
     "DOMPointReadOnly.h",
@@ skipping 20 matching lines @@
     "DOMURLUtilsReadOnly.cpp",
     "DOMURLUtilsReadOnly.h",
     "DatasetDOMStringMap.cpp",
     "DatasetDOMStringMap.h",
     "DecodedDataDocumentParser.cpp",
     "DecodedDataDocumentParser.h",
     "Document.cpp",
     "DocumentEncodingData.cpp",
     "DocumentEncodingData.h",
     "DocumentFragment.cpp",
+    "DocumentFragment.h",
     "DocumentFullscreen.cpp",
     "DocumentFullscreen.h",
     "DocumentInit.cpp",
     "DocumentInit.h",
     "DocumentLifecycle.cpp",
     "DocumentLifecycle.h",
     "DocumentOrShadowRoot.h",
     "DocumentOrderedList.cpp",
     "DocumentOrderedList.h",
     "DocumentOrderedMap.cpp",
+    "DocumentOrderedMap.h",
     "DocumentParser.cpp",
     "DocumentParser.h",
     "DocumentParserTiming.cpp",
     "DocumentParserTiming.h",
     "DocumentStatisticsCollector.cpp",
     "DocumentStatisticsCollector.h",
     "DocumentStyleSheetCollection.cpp",
     "DocumentStyleSheetCollection.h",
     "DocumentStyleSheetCollector.cpp",
     "DocumentStyleSheetCollector.h",
     "DocumentTiming.cpp",
     "DocumentTiming.h",
     "DocumentType.cpp",
+    "DocumentType.h",
     "Element.cpp",
     "Element.h",
     "ElementData.cpp",
     "ElementData.h",
     "ElementDataCache.cpp",
     "ElementDataCache.h",
     "ElementFullscreen.cpp",
     "ElementFullscreen.h",
     "ElementIntersectionObserverData.cpp",
     "ElementIntersectionObserverData.h",
@@ skipping 59 matching lines @@
     "MutationObserver.h",
     "MutationObserverInterestGroup.cpp",
     "MutationObserverInterestGroup.h",
     "MutationObserverRegistration.cpp",
     "MutationObserverRegistration.h",
     "MutationRecord.cpp",
     "MutationRecord.h",
     "NameNodeList.cpp",
     "NameNodeList.h",
     "NamedNodeMap.cpp",
+    "NamedNodeMap.h",
     "Node.cpp",
     "NodeChildRemovalTracker.cpp",
     "NodeChildRemovalTracker.h",
     "NodeComputedStyle.h",
     "NodeFilter.cpp",
     "NodeFilter.h",
     "NodeFilterCondition.h",
     "NodeIterator.cpp",
     "NodeIterator.h",
     "NodeIteratorBase.cpp",
     "NodeIteratorBase.h",
     "NodeListsNodeData.cpp",
     "NodeListsNodeData.h",
     "NodeRareData.cpp",
     "NodeRareData.h",
     "NodeTraversal.cpp",
     "NodeTraversal.h",
     "NodeWithIndex.h",
     "NonDocumentTypeChildNode.h",
     "NonElementParentNode.h",
     "NthIndexCache.cpp",
     "NthIndexCache.h",
     "ParentNode.h",
     "PendingScript.cpp",
+    "PendingScript.h",
     "PresentationAttributeStyle.cpp",
     "PresentationAttributeStyle.h",
     "ProcessingInstruction.cpp",
     "ProcessingInstruction.h",
     "PseudoElement.cpp",
     "PseudoElementData.h",
     "QualifiedName.cpp",
+    "QualifiedName.h",
     "Range.cpp",
     "RawDataDocumentParser.h",
     "RemoteSecurityContext.cpp",
     "RemoteSecurityContext.h",
     "ResizeObservation.cpp",
     "ResizeObservation.h",
     "ResizeObserver.cpp",
     "ResizeObserver.h",
     "ResizeObserverCallback.h",
     "ResizeObserverController.cpp",
@@ skipping 19 matching lines @@
     "SecurityContext.cpp",
     "SecurityContext.h",
     "SelectorQuery.cpp",
     "SelectorQuery.h",
     "ShadowTreeStyleSheetCollection.cpp",
     "ShadowTreeStyleSheetCollection.h",
     "SimulatedClickOptions.h",
     "SinkDocument.cpp",
     "SinkDocument.h",
     "SpaceSplitString.cpp",
+    "SpaceSplitString.h",
     "StaticNodeList.h",
     "StaticRange.cpp",
     "StaticRange.h",
     "StringCallback.h",
     "StyleChangeReason.cpp",
     "StyleChangeReason.h",
     "StyleElement.cpp",
     "StyleElement.h",
     "StyleEngine.cpp",
     "StyleEngine.h",
     "StyleEngineContext.cpp",
     "StyleEngineContext.h",
     "StyleSheetCandidate.cpp",
     "StyleSheetCandidate.h",
     "StyleSheetCollection.cpp",
     "StyleSheetCollection.h",
     "SuspendableObject.cpp",
+    "SuspendableObject.h",
     "SynchronousMutationNotifier.cpp",
     "SynchronousMutationNotifier.h",
     "SynchronousMutationObserver.cpp",
     "SynchronousMutationObserver.h",
     "TagCollection.cpp",
     "TagCollection.h",
     "TaskRunnerHelper.cpp",
     "TaskRunnerHelper.h",
     "Text.cpp",
     "TextLinkColors.cpp",
@@ skipping 113 matching lines @@
     "shadow/SlotAssignment.h",
     "shadow/SlotScopedTraversal.cpp",
     "shadow/SlotScopedTraversal.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }