[linux] Use _GLIBCXX_DEBUG in Debug builds by default for better checking.

build/toolchain.gypi

Index: build/toolchain.gypi
diff --git a/build/toolchain.gypi b/build/toolchain.gypi
index d4a9403cbd7b8b8d13a762c19a1cca157e52c0b9..b8c73177853fa4ac988b8394dbfc633b272d557f 100644
--- a/build/toolchain.gypi
+++ b/build/toolchain.gypi
@@ -61,6 +61,9 @@
     # Similar to the ARM hard float ABI but on MIPS.
     'v8_use_mips_abi_hardfloat%': 'true',
 
+    # Force disable libstdc++ debug mode.
+    'disable_glibcxx_debug%': 0,
+
     'v8_enable_backtrace%': 0,
 
     # Enable profiling support. Only required on Windows.
@@ -1134,6 +1137,11 @@
             # Support for backtrace_symbols.
             'ldflags': [ '-rdynamic' ],
           }],
+          ['OS=="linux" and disable_glibcxx_debug==0', {
+            # Enable libstdc++ debugging facilities to help catch problems
+            # early, see http://crbug.com/65151 .
+            'defines': ['_GLIBCXX_DEBUG=1',],
+          }],
           ['OS=="aix"', {
             'ldflags': [ '-Wl,-bbigtoc' ],
           }],