Split //blimp/client/core to relevant parts.

blimp/client/BUILD.gn

Index: blimp/client/BUILD.gn
diff --git a/blimp/client/BUILD.gn b/blimp/client/BUILD.gn
index 821d7724ed11ef0c85521a0254575cbfa8e11982..676edf52027ffa1677d9919c2df3f36031bfda92 100644
--- a/blimp/client/BUILD.gn
+++ b/blimp/client/BUILD.gn
@@ -408,7 +408,7 @@ if (is_android) {
       ":blimp_java",
       "//base:base_java",
       "//base:base_java_test_support",
-      "//blimp/client/core:core_java",
+      "//blimp/client/core/contents:contents_java",
       "//blimp/client/public:public_headers_java",
       google_play_services_library,
     ]
@@ -416,7 +416,7 @@ if (is_android) {
     java_files = [
       "app/android/javatests/src/org/chromium/blimp/auth/MockTokenSource.java",
       "app/android/javatests/src/org/chromium/blimp/auth/RetryingTokenSourceTest.java",
-      "app/android/javatests/src/org/chromium/blimp/core/BlimpContentsTest.java",
+      "app/android/javatests/src/org/chromium/blimp/core/contents/BlimpContentsTest.java",
       "app/android/javatests/src/org/chromium/blimp/BlimpNativeInstrumentationTestCase.java",
     ]
   }