Remove unused code warnings found by clang.

pdfium.gyp

 {
   'variables': {
     'pdf_use_skia%': 0,
     'conditions': [
       ['OS=="linux"', {
         'bundle_freetype%': 0,
       }, {  # On Android there's no system FreeType. On Windows and Mac, only a
             # few methods are used from it.
         'bundle_freetype%': 1,
       }],
@@ skipping 232 matching lines @@
         'core/src/fpdfapi/fpdf_cmaps/Japan1/cmaps_japan1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/EUC-H_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/EUC-V_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/Ext-RKSJ-H_2.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/Ext-RKSJ-V_2.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/H_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UCS2-HW-H_4.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UCS2-HW-V_4.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UCS2-H_4.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UCS2-V_4.cpp',
-        'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UTF16-H_5.cpp',
-        'core/src/fpdfapi/fpdf_cmaps/Japan1/UniJIS-UTF16-V_5.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Japan1/V_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/Adobe-Korea1-UCS2_2.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/cmaps_korea1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSC-EUC-H_0.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSC-EUC-V_0.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSCms-UHC-HW-H_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSCms-UHC-HW-V_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSCms-UHC-H_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSCms-UHC-V_1.cpp',
         'core/src/fpdfapi/fpdf_cmaps/Korea1/KSCpc-EUC-H_0.cpp',
@@ skipping 489 matching lines @@
         'testing/embedder_test.cpp',
         'testing/embedder_test.h',
         'testing/embedder_test_mock_delegate.h',
         'testing/embedder_test_timer_handling_delegate.h',
         'testing/fx_string_testhelpers.cpp',
         'testing/fx_string_testhelpers.h',
       ],
     },
   ],
 }