Add support to minimize the WebView's memory consumption by default

webkit change is c/148241

bug:5522175

Change-Id: I8562c39c55913ab89848afe8a36e8a2784c12727
diff --git a/src/com/android/browser/WebViewProperties.java b/src/com/android/browser/WebViewProperties.java
index c410038..c662957 100644
--- a/src/com/android/browser/WebViewProperties.java
+++ b/src/com/android/browser/WebViewProperties.java
@@ -19,4 +19,5 @@
     static final String gfxInvertedScreen = "inverted";
     static final String gfxInvertedScreenContrast = "inverted_contrast";
     static final String gfxEnableCpuUploadPath = "enable_cpu_upload_path";
+    static final String gfxUseMinimalMemory = "use_minimal_memory";
 }