Remove a linear search in SkPictureRecord::addTextBlob.

It doesn't seem that harmful to have repeated text blobs in the array
if they occur within the same picture recording. And that does not seem
to be a common occurrence right now anyhow.

BUG=skia:2919
R=fmalita@chromium.org, reed@google.com, mtklein@google.com

Author: jbroman@chromium.org

Review URL: https://codereview.chromium.org/550043003
diff --git a/src/core/SkPictureRecord.cpp b/src/core/SkPictureRecord.cpp
index a6b6f61..b171691 100644
--- a/src/core/SkPictureRecord.cpp
+++ b/src/core/SkPictureRecord.cpp
@@ -1544,12 +1544,9 @@
 }
 
 void SkPictureRecord::addTextBlob(const SkTextBlob *blob) {
-    int index = fTextBlobRefs.find(blob);
-    if (index < 0) {    // not found
-        index = fTextBlobRefs.count();
-        *fTextBlobRefs.append() = blob;
-        blob->ref();
-    }
+    int index = fTextBlobRefs.count();
+    *fTextBlobRefs.append() = blob;
+    blob->ref();
     // follow the convention of recording a 1-based index
     this->addInt(index + 1);
 }