Replace PST Report with buffer

Merge from Widevine repo of http://go/wvgerrit/23044

On some platforms, the compiler will not pack structures.  This CL
replaces the OECrypto_PST_Report packed structure with a simple buffer
of uint8_t.  This changes the signature of OEMCrypto_ReportUsage as
part of OEMCrypto v13.

There is also a new wrapper class that test code, the mock, and debug
code can use to access data in the report.

The old packed structure definition is moved to the level 3, where we
use a compiler that packs sructs when asked nicely.

arm/libwvlevel3.a  Level3 Library 4445 Jan 20 2017 11:29:15
x86/libwvlevel3.a  Level3 Library 4464 Jan 20 2017 11:10:49
mips/libwvlevel3.a  Level3 Library 4465 Jan 20 2017 10:56:08

b/32180083

Change-Id: Ie138f034cb12780a2f8636888cebf022c52169e5

libwvdrmengine/oemcrypto/include/OEMCryptoCENC.h

@@ -249,7 +249,12 @@ typedef enum OEMCrypto_Usage_Entry_Status {
 
 /*
  * OEMCrypto_PST_Report is used to report an entry from the Usage Table.
+ *
+ * Platforms that have compilers that support packed structures, may use the
+ * following definition.  Other platforms may use the header pst_report.h which
+ * defines a wrapper class.
  */
+#if 0  // If your compiler supports __attribute__((packed)).
 typedef struct {
   uint8_t signature[20];  //  -- HMAC SHA1 of the rest of the report.
   uint8_t status;  // current status of entry. (OEMCrypto_Usage_Entry_Status)
@@ -261,6 +266,7 @@ typedef struct {
   int64_t seconds_since_last_decrypt;      // now - time_of_last_decrypt
   uint8_t pst[];
 } __attribute__((packed)) OEMCrypto_PST_Report;
+#endif
 
 /*
  *  OEMCrypto_Clock_Security_Level.
@@ -2696,7 +2702,7 @@ OEMCryptoResult OEMCrypto_DeactivateUsageEntry(OEMCrypto_SESSION session,
 /* TODO(fredgc): copy text from http://go/wvgerrit/22887 */
 OEMCryptoResult OEMCrypto_ReportUsage(OEMCrypto_SESSION session,
                                       const uint8_t* pst, size_t pst_length,
-                                      OEMCrypto_PST_Report* buffer,
+                                      uint8_t* buffer,
                                       size_t* buffer_length);
 
 /*