Add command_line to SystemInfo data structure.

third_party/WebKit/Source/core/inspector/browser_protocol.json

Index: third_party/WebKit/Source/core/inspector/browser_protocol.json
diff --git a/third_party/WebKit/Source/core/inspector/browser_protocol.json b/third_party/WebKit/Source/core/inspector/browser_protocol.json
index 0060d55ef89f30e039effde25b5e314377b9e6e6..a88f4d115fdb2a70fdaf014da78fa7c45c2d4951 100644
--- a/third_party/WebKit/Source/core/inspector/browser_protocol.json
+++ b/third_party/WebKit/Source/core/inspector/browser_protocol.json
@@ -4582,7 +4582,8 @@
                 "returns": [
                     { "name": "gpu", "$ref": "GPUInfo", "description": "Information about the GPUs on the system." },
                     { "name": "modelName", "type": "string", "description": "A platform-dependent description of the model of the machine. On Mac OS, this is, for example, 'MacBookPro'. Will be the empty string if not supported." },
-                    { "name": "modelVersion", "type": "string", "description": "A platform-dependent description of the version of the machine. On Mac OS, this is, for example, '10.1'. Will be the empty string if not supported." }
+                    { "name": "modelVersion", "type": "string", "description": "A platform-dependent description of the version of the machine. On Mac OS, this is, for example, '10.1'. Will be the empty string if not supported." },
+                    { "name": "commandLine", "type": "string", "description": "The command line string used to launch the browser. Will be the empty string if not supported." }
                 ]
             }
         ]