Nuke WebPassOwnPtr<T> and replace it with std::unique_ptr<T>.

third_party/WebKit/Source/wtf/wtf.gypi

 # For GN compatibility, this file can not have any conditions.
 {
     'variables': {
         'wtf_files': [
             'ASCIICType.cpp',
             'ASCIICType.h',
             'AddressSanitizer.h',
             'AddressSpaceRandomization.cpp',
             'AddressSpaceRandomization.h',
             'Alignment.h',
@@ skipping 73 matching lines @@
             'PartitionAlloc.cpp',
             'PartitionAlloc.h',
             'PartitionAllocator.cpp',
             'PartitionAllocator.h',
             'Partitions.cpp',
             'Partitions.h',
             'PassOwnPtr.h',
             'PassRefPtr.h',
             'PrintStream.cpp',
             'PrintStream.h',
+            'PtrUtil.h',
             'RefCounted.h',
             'RefCountedLeakCounter.cpp',
             'RefCountedLeakCounter.h',
             'RefPtr.h',
             'RetainPtr.h',
             'SaturatedArithmetic.h',
             'SizeLimits.cpp',
             'SpinLock.cpp',
             'SpinLock.h',
             'StaticConstructors.h',
@@ skipping 120 matching lines @@
             'text/StringBufferTest.cpp',
             'text/StringBuilderTest.cpp',
             'text/StringImplTest.cpp',
             'text/StringOperatorsTest.cpp',
             'text/TextCodecReplacementTest.cpp',
             'text/TextCodecUTF8Test.cpp',
             'text/WTFStringTest.cpp',
         ],
     },
 }