Move plugin_browsertests.cc from browser_tests to content_browsertests.

content/test/browser_test_base.h

Index: content/test/browser_test_base.h
===================================================================
--- content/test/browser_test_base.h	(revision 147965)
+++ content/test/browser_test_base.h	(working copy)
@@ -8,6 +8,8 @@
 #include "base/compiler_specific.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+class CommandLine;
+
 class BrowserTestBase : public testing::Test {
  public:
   BrowserTestBase();
@@ -25,6 +27,14 @@
   // Restores state configured in SetUp.
   virtual void TearDown() OVERRIDE;
 
+  // Override this to add any custom setup code that needs to be done on the
+  // main thread after the browser is created and just before calling
+  // RunTestOnMainThread().
+  virtual void SetUpOnMainThread() {}
+
+  // Override this to add command line flags specific to your test.
+  virtual void SetUpCommandLine(CommandLine* command_line) {}
+
  protected:
   // We need these special methods because SetUp is the bottom of the stack
   // that winds up calling your test method, so it is not always an option