Add namespace and re-arrange PDFium's local copy of chromium /base.

third_party/BUILD.gn

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 group("third_party") {
   deps = [
     ":bigint",
     ":freetype",
-    ":safemath",
+    ":pdfium_base",
   ]
 }
 
 static_library("bigint") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
       "//third_party/pdfium:pdfium_config",
       "//build/config/compiler:no_chromium_code",
   ]
   sources = [
@@ skipping 42 matching lines @@
     "freetype/src/psnames/psmodule.c",
     "freetype/src/raster/raster.c",
     "freetype/src/sfnt/sfnt.c",
     "freetype/src/smooth/smooth.c",
     "freetype/src/truetype/truetype.c",
     "freetype/src/type1/type1.c",
     "freetype/src/cid/type1cid.c",
   ]
 }
 
-component("safemath") {
+component("pdfium_base") {
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
       "//third_party/pdfium:pdfium_config",
       "//build/config/compiler:no_chromium_code",
   ]
   sources = [
-    "logging.h",
-    "macros.h",
-    "template_util.h",
-    "numerics/safe_conversions.h",
-    "numerics/safe_conversions_impl.h",
-    "numerics/safe_math.h",
-    "numerics/safe_math_impl.h",
+    "base/logging.h",
+    "base/macros.h",
+    "base/template_util.h",
+    "base/numerics/safe_conversions.h",
+    "base/numerics/safe_conversions_impl.h",
+    "base/numerics/safe_math.h",
+    "base/numerics/safe_math_impl.h",
   ]
 }