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/layout/BUILD.gn

Index: third_party/WebKit/Source/core/layout/BUILD.gn
diff --git a/third_party/WebKit/Source/core/layout/BUILD.gn b/third_party/WebKit/Source/core/layout/BUILD.gn
index f62e8461df08a5b02af18f836f267f247c66f467..0492231385badc8124093c4327335f00e5f0b55a 100644
--- a/third_party/WebKit/Source/core/layout/BUILD.gn
+++ b/third_party/WebKit/Source/core/layout/BUILD.gn
@@ -32,6 +32,7 @@ blink_core_sources("layout") {
     "HitTestCache.cpp",
     "HitTestCache.h",
     "HitTestCanvasResult.cpp",
+    "HitTestCanvasResult.h",
     "HitTestLocation.cpp",
     "HitTestLocation.h",
     "HitTestResult.cpp",
@@ -45,10 +46,12 @@ blink_core_sources("layout") {
     "LayoutAnalyzer.h",
     "LayoutBR.cpp",
     "LayoutBlock.cpp",
+    "LayoutBlock.h",
     "LayoutBlockFlow.cpp",
     "LayoutBlockFlowLine.cpp",
     "LayoutBox.cpp",
     "LayoutBoxModelObject.cpp",
+    "LayoutBoxModelObject.h",
     "LayoutButton.cpp",
     "LayoutButton.h",
     "LayoutCounter.cpp",
@@ -58,6 +61,7 @@ blink_core_sources("layout") {
     "LayoutDetailsMarker.cpp",
     "LayoutDetailsMarker.h",
     "LayoutEmbeddedObject.cpp",
+    "LayoutEmbeddedObject.h",
     "LayoutFieldset.cpp",
     "LayoutFieldset.h",
     "LayoutFileUploadControl.cpp",
@@ -82,13 +86,17 @@ blink_core_sources("layout") {
     "LayoutIFrame.cpp",
     "LayoutIFrame.h",
     "LayoutImage.cpp",
+    "LayoutImage.h",
     "LayoutImageResource.cpp",
+    "LayoutImageResource.h",
     "LayoutImageResourceStyleImage.cpp",
+    "LayoutImageResourceStyleImage.h",
     "LayoutInline.cpp",
     "LayoutInline.h",
     "LayoutListBox.cpp",
     "LayoutListBox.h",
     "LayoutListItem.cpp",
+    "LayoutListItem.h",
     "LayoutListMarker.cpp",
     "LayoutListMarker.h",
     "LayoutMedia.cpp",
@@ -103,14 +111,17 @@ blink_core_sources("layout") {
     "LayoutMultiColumnSpannerPlaceholder.h",
     "LayoutObject.cpp",
     "LayoutObjectChildList.cpp",
+    "LayoutObjectChildList.h",
     "LayoutPagedFlowThread.cpp",
     "LayoutPagedFlowThread.h",
     "LayoutPart.cpp",
+    "LayoutPart.h",
     "LayoutProgress.cpp",
     "LayoutProgress.h",
     "LayoutQuote.cpp",
     "LayoutQuote.h",
     "LayoutReplaced.cpp",
+    "LayoutReplaced.h",
     "LayoutRuby.cpp",
     "LayoutRuby.h",
     "LayoutRubyBase.cpp",
@@ -134,6 +145,7 @@ blink_core_sources("layout") {
     "LayoutSliderThumb.cpp",
     "LayoutSliderThumb.h",
     "LayoutState.cpp",
+    "LayoutState.h",
     "LayoutTable.cpp",
     "LayoutTable.h",
     "LayoutTableBoxComponent.cpp",
@@ -177,6 +189,7 @@ blink_core_sources("layout") {
     "LayoutVideo.cpp",
     "LayoutVideo.h",
     "LayoutView.cpp",
+    "LayoutView.h",
     "LayoutWordBreak.cpp",
     "LayoutWordBreak.h",
     "ListMarkerText.cpp",
@@ -191,6 +204,7 @@ blink_core_sources("layout") {
     "PointerEventsHitRules.cpp",
     "PointerEventsHitRules.h",
     "ScrollAlignment.cpp",
+    "ScrollAlignment.h",
     "ScrollAnchor.cpp",
     "ScrollAnchor.h",
     "SubtreeLayoutScope.cpp",
@@ -274,6 +288,7 @@ blink_core_sources("layout") {
     "line/InlineIterator.h",
     "line/InlineTextBox.cpp",
     "line/LineBoxList.cpp",
+    "line/LineBoxList.h",
     "line/LineBreaker.cpp",
     "line/LineBreaker.h",
     "line/LineWidth.cpp",