Move session into //blimp/client/app and update GN files.

blimp/client/core/contents/BUILD.gn

Index: blimp/client/core/contents/BUILD.gn
diff --git a/blimp/client/core/contents/BUILD.gn b/blimp/client/core/contents/BUILD.gn
index fa0f735248119fc3af5866518a528d27f7bb6e1b..62c4412a5b755c642a9d2ca1315024edc3d1c8b5 100644
--- a/blimp/client/core/contents/BUILD.gn
+++ b/blimp/client/core/contents/BUILD.gn
@@ -8,7 +8,10 @@ if (is_android) {
 }
 
 source_set("contents") {
-  visibility = [ "//blimp/client/*" ]
+  visibility = [
+    "//blimp/client/app:*",  # TODO(nyquist): Remove this. See crbug/651964.
+    "//blimp/client/core/*",
+  ]
 
   sources = [
     "blimp_contents_impl.cc",
@@ -82,6 +85,11 @@ source_set("contents") {
 }
 
 source_set("test_support") {
+  visibility = [
+    "//blimp/engine:browser_tests",
+    "//blimp/client/core/contents:unit_tests",
+  ]
+
   testonly = true
 
   sources = [
@@ -143,7 +151,10 @@ source_set("unit_tests") {
 
 if (is_android) {
   android_library("contents_java") {
-    visibility = [ "//blimp/client/*" ]
+    visibility = [
+      "//blimp/client/app:*",  # TODO(nyquist): Remove this. See crbug/651964.
+      "//blimp/client/core/*",
+    ]
 
     java_files = [
       "android/java/src/org/chromium/blimp/core/contents/BlimpContentsImpl.java",
@@ -156,7 +167,7 @@ if (is_android) {
 
     deps = [
       "//base:base_java",
-      "//blimp/client:blimp_java_resources",
+      "//blimp/client/app:blimp_java_resources",
       "//blimp/client/public:public_headers_java",
       "//third_party/android_tools:android_support_v7_appcompat_java",
       "//ui/android:ui_java",