ahat: add support for diffing two heap dumps.

ahat now has the option to specify a --baseline hprof file to use as
the basis for comparing two heap dumps. When a baseline hprof file is
provided, ahat will highlight how the heap dump has changed relative
to the hprof file.

Differences that are highlighted include:
* overall heap sizes
* total bytes and number of allocations by type
* new and deleted instances of a given type
* retained sizes of objects
* instance fields, static fields, and array elements of modified objects

Also:
* Remove support for showing NativeAllocations, because I haven't ever
  found it to be useful, it is not obvious what a "native" allocation
  is, and I don't feel like adding diff support for them.
* Remove help page. Because it is outdated, not well maintained, and
  not very helpful in the first place.

Test: m ahat-test
Test: Run in diff mode for tests and added new tests for diff.
Test: Manually run with and without diff mode on heap dumps from system server.
Bug: 33770653
Change-Id: Id9a392ac75588200e716bbc3edbae6e9cd97c26b

1 files changed, 0 insertions, 49 deletions

diff --git a/tools/ahat/src/heapdump/AhatClassInstance.java b/tools/ahat/src/heapdump/AhatClassInstance.java
index fae34b0d29..273530af64 100644
--- a/tools/ahat/src/heapdump/AhatClassInstance.java
+++ b/tools/ahat/src/heapdump/AhatClassInstance.java
@@ -143,55 +143,6 @@ public class AhatClassInstance extends AhatInstance {
     return null;
   }
 
-  @Override public NativeAllocation getNativeAllocation() {
-    if (!isInstanceOfClass("libcore.util.NativeAllocationRegistry$CleanerThunk")) {
-      return null;
-    }
-
-    Long pointer = getLongField("nativePtr", null);
-    if (pointer == null) {
-      return null;
-    }
-
-    // Search for the registry field of inst.
-    AhatInstance registry = null;
-    for (FieldValue field : mFieldValues) {
-      Value fieldValue = field.getValue();
-      if (fieldValue.isAhatInstance()) {
-        AhatClassInstance fieldInst = fieldValue.asAhatInstance().asClassInstance();
-        if (fieldInst != null
-            && fieldInst.isInstanceOfClass("libcore.util.NativeAllocationRegistry")) {
-          registry = fieldInst;
-          break;
-        }
-      }
-    }
-
-    if (registry == null || !registry.isClassInstance()) {
-      return null;
-    }
-
-    Long size = registry.asClassInstance().getLongField("size", null);
-    if (size == null) {
-      return null;
-    }
-
-    AhatInstance referent = null;
-    for (AhatInstance ref : getHardReverseReferences()) {
-      if (ref.isClassInstance() && ref.asClassInstance().isInstanceOfClass("sun.misc.Cleaner")) {
-        referent = ref.getReferent();
-        if (referent != null) {
-          break;
-        }
-      }
-    }
-
-    if (referent == null) {
-      return null;
-    }
-    return new NativeAllocation(size, getHeap(), pointer, referent);
-  }
-
   @Override public String getDexCacheLocation(int maxChars) {
     if (isInstanceOfClass("java.lang.DexCache")) {
       AhatInstance location = getRefField("location");