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 Because it is outdated, not well maintained, and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, 72 insertions, 1 deletions

diff --git a/tools/ahat/src/DocString.java b/tools/ahat/src/DocString.java
index 19666dea8c..c6303c8c35 100644
--- a/tools/ahat/src/DocString.java
+++ b/tools/ahat/src/DocString.java
@@ -53,7 +53,6 @@ class DocString {
   public static DocString link(URI uri, DocString content) {
     DocString doc = new DocString();
     return doc.appendLink(uri, content);
-
   }
 
   /**
@@ -86,6 +85,78 @@ class DocString {
     return this;
   }
 
+  /**
+   * Adorn the given string to indicate it represents something added relative
+   * to a baseline.
+   */
+  public static DocString added(DocString str) {
+    DocString string = new DocString();
+    string.mStringBuilder.append("<span class=\"added\">");
+    string.mStringBuilder.append(str.html());
+    string.mStringBuilder.append("</span>");
+    return string;
+  }
+
+  /**
+   * Adorn the given string to indicate it represents something added relative
+   * to a baseline.
+   */
+  public static DocString added(String str) {
+    return added(text(str));
+  }
+
+  /**
+   * Adorn the given string to indicate it represents something removed relative
+   * to a baseline.
+   */
+  public static DocString removed(DocString str) {
+    DocString string = new DocString();
+    string.mStringBuilder.append("<span class=\"removed\">");
+    string.mStringBuilder.append(str.html());
+    string.mStringBuilder.append("</span>");
+    return string;
+  }
+
+  /**
+   * Adorn the given string to indicate it represents something removed relative
+   * to a baseline.
+   */
+  public static DocString removed(String str) {
+    return removed(text(str));
+  }
+
+  /**
+   * Standard formatted DocString for describing a change in size relative to
+   * a baseline.
+   * @param noCurrent - whether no current object exists.
+   * @param noBaseline - whether no basline object exists.
+   * @param current - the size of the current object.
+   * @param baseline - the size of the baseline object.
+   */
+  public static DocString delta(boolean noCurrent, boolean noBaseline,
+      long current, long baseline) {
+    DocString doc = new DocString();
+    return doc.appendDelta(noCurrent, noBaseline, current, baseline);
+  }
+
+  /**
+   * Standard formatted DocString for describing a change in size relative to
+   * a baseline.
+   */
+  public DocString appendDelta(boolean noCurrent, boolean noBaseline,
+      long current, long baseline) {
+    if (noCurrent) {
+      append(removed(format("%+,14d", 0 - baseline)));
+    } else if (noBaseline) {
+      append(added("new"));
+    } else if (current > baseline) {
+      append(added(format("%+,14d", current - baseline)));
+    } else if (current < baseline) {
+      append(removed(format("%+,14d", current - baseline)));
+    }
+    return this;
+  }
+
   public DocString appendLink(URI uri, DocString content) {
     mStringBuilder.append("<a href=\"");
     mStringBuilder.append(uri.toASCIIString());