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/css/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("css") {
   split_count = 5
   sources = [
     "ActiveStyleSheets.cpp",
     "ActiveStyleSheets.h",
     "BasicShapeFunctions.cpp",
+    "BasicShapeFunctions.h",
     "BinaryDataFontFaceSource.cpp",
     "BinaryDataFontFaceSource.h",
     "CSSBasicShapeValues.cpp",
+    "CSSBasicShapeValues.h",
     "CSSBorderImage.cpp",
     "CSSBorderImage.h",
     "CSSBorderImageSliceValue.cpp",
     "CSSBorderImageSliceValue.h",
     "CSSCalculationValue.cpp",
     "CSSCalculationValue.h",
     "CSSColorValue.cpp",
     "CSSColorValue.h",
     "CSSComputedStyleDeclaration.cpp",
+    "CSSComputedStyleDeclaration.h",
     "CSSConditionRule.cpp",
     "CSSConditionRule.h",
     "CSSContentDistributionValue.cpp",
     "CSSContentDistributionValue.h",
     "CSSCounterValue.cpp",
     "CSSCounterValue.h",
     "CSSCrossfadeValue.cpp",
     "CSSCrossfadeValue.h",
     "CSSCursorImageValue.cpp",
+    "CSSCursorImageValue.h",
     "CSSCustomFontData.h",
     "CSSCustomIdentValue.cpp",
     "CSSCustomIdentValue.h",
     "CSSCustomPropertyDeclaration.cpp",
     "CSSCustomPropertyDeclaration.h",
     "CSSDefaultStyleSheets.cpp",
     "CSSDefaultStyleSheets.h",
     "CSSFontFace.cpp",
     "CSSFontFace.h",
     "CSSFontFaceRule.cpp",
@@ skipping 21 matching lines @@
     "CSSGridAutoRepeatValue.h",
     "CSSGridLineNamesValue.cpp",
     "CSSGridLineNamesValue.h",
     "CSSGridTemplateAreasValue.cpp",
     "CSSGridTemplateAreasValue.h",
     "CSSGroupingRule.cpp",
     "CSSGroupingRule.h",
     "CSSIdentifierValue.cpp",
     "CSSIdentifierValue.h",
     "CSSImageGeneratorValue.cpp",
+    "CSSImageGeneratorValue.h",
     "CSSImageSetValue.cpp",
+    "CSSImageSetValue.h",
     "CSSImageValue.cpp",
+    "CSSImageValue.h",
     "CSSImportRule.cpp",
     "CSSImportRule.h",
     "CSSInheritedValue.cpp",
     "CSSInheritedValue.h",
     "CSSInitialValue.cpp",
     "CSSInitialValue.h",
     "CSSKeyframeRule.cpp",
     "CSSKeyframeRule.h",
     "CSSKeyframesRule.cpp",
     "CSSKeyframesRule.h",
@@ skipping 12 matching lines @@
     "CSSPaintValue.cpp",
     "CSSPaintValue.h",
     "CSSPathValue.cpp",
     "CSSPathValue.h",
     "CSSPendingSubstitutionValue.cpp",
     "CSSPendingSubstitutionValue.h",
     "CSSPrimitiveValue.cpp",
     "CSSPrimitiveValue.h",
     "CSSPrimitiveValueMappings.h",
     "CSSProperty.cpp",
+    "CSSProperty.h",
     "CSSPropertyEquality.cpp",
     "CSSPropertyEquality.h",
     "CSSPropertySourceData.cpp",
+    "CSSPropertySourceData.h",
     "CSSQuadValue.cpp",
     "CSSQuadValue.h",
     "CSSReflectValue.cpp",
+    "CSSReflectValue.h",
     "CSSRule.cpp",
     "CSSRule.h",
     "CSSRuleList.cpp",
     "CSSRuleList.h",
     "CSSSegmentedFontFace.cpp",
     "CSSSegmentedFontFace.h",
     "CSSSelector.cpp",
+    "CSSSelector.h",
     "CSSSelectorList.cpp",
     "CSSSelectorList.h",
     "CSSShadowValue.cpp",
     "CSSShadowValue.h",
     "CSSStringValue.cpp",
     "CSSStringValue.h",
     "CSSStyleDeclaration.cpp",
     "CSSStyleDeclaration.h",
     "CSSStyleRule.cpp",
     "CSSStyleRule.h",
     "CSSStyleSheet.cpp",
     "CSSStyleSheet.h",
     "CSSSupportsRule.cpp",
     "CSSSupportsRule.h",
     "CSSSyntaxDescriptor.cpp",
     "CSSSyntaxDescriptor.h",
     "CSSTiming.cpp",
     "CSSTiming.h",
     "CSSTimingFunctionValue.cpp",
     "CSSTimingFunctionValue.h",
     "CSSToLengthConversionData.cpp",
     "CSSToLengthConversionData.h",
     "CSSURIValue.cpp",
     "CSSURIValue.h",
     "CSSUnicodeRangeValue.cpp",
     "CSSUnicodeRangeValue.h",
     "CSSUnsetValue.cpp",
     "CSSUnsetValue.h",
     "CSSValue.cpp",
+    "CSSValue.h",
     "CSSValueIDMappings.h",
     "CSSValueList.cpp",
+    "CSSValueList.h",
     "CSSValuePair.cpp",
     "CSSValuePair.h",
     "CSSValuePool.cpp",
     "CSSValuePool.h",
     "CSSVariableData.cpp",
     "CSSVariableData.h",
     "CSSVariableReferenceValue.cpp",
     "CSSVariableReferenceValue.h",
     "CSSViewportRule.cpp",
     "CSSViewportRule.h",
@@ skipping 31 matching lines @@
     "MediaQueryExp.cpp",
     "MediaQueryExp.h",
     "MediaQueryList.cpp",
     "MediaQueryList.h",
     "MediaQueryListEvent.h",
     "MediaQueryListListener.cpp",
     "MediaQueryListListener.h",
     "MediaQueryMatcher.cpp",
     "MediaQueryMatcher.h",
     "MediaValues.cpp",
+    "MediaValues.h",
     "MediaValuesCached.cpp",
+    "MediaValuesCached.h",
     "MediaValuesDynamic.cpp",
+    "MediaValuesDynamic.h",
     "MediaValuesInitialViewport.cpp",
     "MediaValuesInitialViewport.h",
     "PageRuleCollector.cpp",
     "PageRuleCollector.h",
     "PropertyRegistration.cpp",
     "PropertyRegistration.h",
     "PropertyRegistry.cpp",
     "PropertyRegistry.h",
     "PropertySetCSSStyleDeclaration.cpp",
     "PropertySetCSSStyleDeclaration.h",
@@ skipping 103 matching lines @@
     "parser/CSSParser.cpp",
     "parser/CSSParser.h",
     "parser/CSSParserContext.cpp",
     "parser/CSSParserContext.h",
     "parser/CSSParserFastPaths.cpp",
     "parser/CSSParserFastPaths.h",
     "parser/CSSParserImpl.cpp",
     "parser/CSSParserImpl.h",
     "parser/CSSParserMode.h",
     "parser/CSSParserObserverWrapper.cpp",
+    "parser/CSSParserObserverWrapper.h",
     "parser/CSSParserSelector.cpp",
     "parser/CSSParserSelector.h",
     "parser/CSSParserToken.cpp",
+    "parser/CSSParserToken.h",
     "parser/CSSParserTokenRange.cpp",
     "parser/CSSParserTokenRange.h",
     "parser/CSSPropertyParser.cpp",
     "parser/CSSPropertyParser.h",
     "parser/CSSPropertyParserHelpers.cpp",
     "parser/CSSPropertyParserHelpers.h",
     "parser/CSSSelectorParser.cpp",
     "parser/CSSSelectorParser.h",
     "parser/CSSSupportsParser.cpp",
     "parser/CSSSupportsParser.h",
     "parser/CSSTokenizer.cpp",
+    "parser/CSSTokenizer.h",
     "parser/CSSTokenizerInputStream.cpp",
+    "parser/CSSTokenizerInputStream.h",
     "parser/CSSVariableParser.cpp",
     "parser/CSSVariableParser.h",
     "parser/FontVariantLigaturesParser.h",
     "parser/FontVariantNumericParser.h",
     "parser/MediaQueryBlockWatcher.cpp",
+    "parser/MediaQueryBlockWatcher.h",
     "parser/MediaQueryParser.cpp",
+    "parser/MediaQueryParser.h",
     "parser/SizesAttributeParser.cpp",
+    "parser/SizesAttributeParser.h",
     "parser/SizesCalcParser.cpp",
+    "parser/SizesCalcParser.h",
     "properties/CSSPropertyAPIAlignItems.cpp",
     "properties/CSSPropertyAPIAlignOrJustifyContent.cpp",
     "properties/CSSPropertyAPIAlignOrJustifySelf.cpp",
     "properties/CSSPropertyAPIBaselineShift.cpp",
     "properties/CSSPropertyAPIBorderImageOutset.cpp",
     "properties/CSSPropertyAPIBorderImageRepeat.cpp",
     "properties/CSSPropertyAPIBorderImageSlice.cpp",
     "properties/CSSPropertyAPIBorderImageWidth.cpp",
     "properties/CSSPropertyAPIBorderRadius.cpp",
     "properties/CSSPropertyAPIBorderWidth.cpp",
@@ skipping 152 matching lines @@
     "resolver/TransformBuilder.h",
     "resolver/ViewportStyleResolver.cpp",
     "resolver/ViewportStyleResolver.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }