Add a BrowserViewRenderer unittest for compositor switch logic

content/public/test/test_synchronous_compositor_android.cc

Index: content/public/test/test_synchronous_compositor_android.cc
diff --git a/content/public/test/test_synchronous_compositor_android.cc b/content/public/test/test_synchronous_compositor_android.cc
index 7f9bd2359b6402096882db250c11a7ae07065f0f..b47d28688ce127f3f567dfdc05c6f49e1cf55487 100644
--- a/content/public/test/test_synchronous_compositor_android.cc
+++ b/content/public/test/test_synchronous_compositor_android.cc
@@ -10,20 +10,19 @@
 
 namespace content {
 
-TestSynchronousCompositor::TestSynchronousCompositor() : client_(NULL) {
-}
+TestSynchronousCompositor::TestSynchronousCompositor(int process_id,
+                                                     int routing_id)
+    : client_(NULL), process_id_(process_id), routing_id_(routing_id) {}
 
 TestSynchronousCompositor::~TestSynchronousCompositor() {
+  client_->DidDestroyCompositor(this, process_id_, routing_id_);
   SetClient(NULL);
 }
 
 void TestSynchronousCompositor::SetClient(SynchronousCompositorClient* client) {
-  if (client_)
-    client_->DidDestroyCompositor(this, 0, 0);
   client_ = client;
-  if (client_) {
-    client_->DidInitializeCompositor(this, 0, 0);
-  }
+  if (client_)
+    client_->DidInitializeCompositor(this, process_id_, routing_id_);

[boliu, 2016/06/21 17:29:47]

did you have to rearrange this logic?

[hush (inactive), 2016/06/21 21:27:26]

well it's saner. And... it is better to separate them so that we can have a
state where there are 2 compositors alive, but one "active"
And you do need a place to notify the destruction of the current compositor,
otherwise the compositor_map_.empty() dcheck in ~BrowserViewRenderer won't pass.

[boliu, 2016/06/21 21:31:59]

Didn't SetClient(NULL) used to call DidDestroyCompositor though?

[hush (inactive), 2016/06/21 22:02:27]

ok. I reverted this bit.

 }
 
 SynchronousCompositor::Frame TestSynchronousCompositor::DemandDrawHw(