Hook up symbol files to the Windows GN build.

build/toolchain/win/BUILD.gn

Index: build/toolchain/win/BUILD.gn
diff --git a/build/toolchain/win/BUILD.gn b/build/toolchain/win/BUILD.gn
index 3f0d0d76262cd37fd10a750445bfc8cd9248029d..143aa0a0e293c9f13f48a1d1ccc85b3b0f6ea8a9 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -22,6 +22,11 @@ exec_script("setup_toolchain.py",
 stamp_command = "$python_path gyp-win-tool stamp \$out"
 copy_command = "$python_path gyp-win-tool recursive-mirror \$in \$out"
 
+# MSVC can't share PDB files between compilers compiling C and C++ files, so
+# we construct different names for each type.
+c_pdb_suffix = " /Fd\${target_out_dir}/\${target_name}_c.pdb"
+cc_pdb_suffix = " /Fd\${target_out_dir}/\${target_name}_cc.pdb"
+
 # 32-bit toolchain -------------------------------------------------------------
 
 toolchain("32") {
@@ -29,16 +34,16 @@ toolchain("32") {
   lib_prefix = ""
   lib_dir_prefix="/LIBPATH:"
 
-  cc_command = "ninja -t msvc -e environment.x86 -- cl.exe /nologo /showIncludes /FC @\$out.rsp /c \$in /Fo\$out /Fd\$pdbname"
+  cc_command = "ninja -t msvc -e environment.x86 -- cl.exe /nologo /showIncludes /FC @\$out.rsp /c \$in /Fo\$out"
   tool("cc") {
-    command = cc_command
+    command = cc_command + c_pdb_suffix
     description = "CC \$out"
     rspfile = "\$out.rsp"
     rspfile_content = "\$defines \$includes \$cflags \$cflags_c"
     depsformat = "msvc"
   }
   tool("cxx") {
-    command = cc_command  # Same as above
+    command = cc_command + cc_pdb_suffix
     description = "CXX \$out"
     rspfile = "\$out.rsp"
     rspfile_content = "\$defines \$includes \$cflags \$cflags_cc"
@@ -88,16 +93,16 @@ toolchain("64") {
   lib_prefix = ""
   lib_dir_prefix="/LIBPATH:"
 
-  cc_command = "ninja -t msvc -e environment.x64 -- cl.exe /nologo /showIncludes /FC @\$out.rsp /c \$in /Fo\$out /Fd\$pdbname"
+  cc_command = "ninja -t msvc -e environment.x64 -- cl.exe /nologo /showIncludes /FC @\$out.rsp /c \$in /Fo\$out"
   tool("cc") {
-    command = cc_command
+    command = cc_command + c_pdb_suffix
     description = "CC \$out"
     rspfile = "\$out.rsp"
     rspfile_content = "\$defines \$includes \$cflags \$cflags_c"
     depsformat = "msvc"
   }
   tool("cxx") {
-    command = cc_command  # Same as above
+    command = cc_command + cc_pdb_suffix
     description = "CXX \$out"
     rspfile = "\$out.rsp"
     rspfile_content = "\$defines \$includes \$cflags \$cflags_cc"